Why do you play 2. Bc4 against the Sicilian?

Two-year-olds do this as well.

There are 2 different things - choosing an opening based on a minuscule difference in engine evaluation is silly, but there are some objective truths we use to guide us, aren't there? We do not start the game of chess by playing 1. f3, because this move is objectively bad. 

2. Bc4 against the Sicilian is not bad because of the engine evaluation. Even here in this thread people explained how the bishop gets blunted by e7-e6 and how Black easily achieves d7-d5 - a move that is often a distant dream in many lines of the Sicilian. So it is not just the engine score. There are valid chess principles and ideas here. And they all scream "don't play 2. Bc4!". Yet people do.

@66

"2. Bc4 is worse than some other moves against the Sicilian, PERIOD."
++ That is false, PERIOD.
Look yourself at any engine: everything gives 0.0 if you calculate long enough.
1 e4 c5 2 Nf3 has a better reputation than 1 e4 c5 2 Bc4 in the same sense that 1 d4 Nf6 2 c4 has a better reputation than 1 d4 Nf6 2 Bf4. It is all playable and objectively neither inferior nor superior.

@69

"We do not start the game of chess by playing 1. f3, because this move is objectively bad."
++ But 1 e4 c5 2 Bc4 is not objectively bad. GM Van Foreest played 2 Bc4 against GM Rameshbabu Praggnanandhaa because he thought that gave him the best practical chance, and he was right: he won. If he had chosen 2 Nf3, then it may have been a draw or even a loss.

"the bishop gets blunted by e7-e6 and how Black easily achieves d7-d5"
++ That transposes to a Nimzovich Indian Defence reversed with an extra tempo.

"There are valid chess principles and ideas here."
++ The only objection is that Bc4 develops a bishop before the knight, just like 1 d4 d5/Nf6 2 Bf4 violates that same principle, but gets played at top level nevertheless.

"And they all scream don't play 2. Bc4!" ++ Only you do.

"Yet people do."
++ These people know that it gives good practical chances, e.g. GM Van Foreest.

I gave it a go against the 2200 "Noam" bot here on chess.com (one of my favorite bot sparring partners):

My conclusion: 2. Bc4 is certainly playable.

Back when I first began learning chess, one of the first lessons that I was taught: the main point of the opening phase is to reach a playable middle-game. Not "perfect" or "engine-accurate" or "theoretically-approved", but: ... playable.

It's true that 2. Bc4 is a less principled, and less forcing try against the Sicilian. But it's still a viable approach - especially in capable hands.

And black is almost certainly going to be less prepared against it - which means white will battle against less engine prep from black, and that the onus is put on black, earlier on, to use his own brain to play ...

Yes, this was your OP, basically. Couple of points here.

1. So far nobody has admitted to playing 2.Bc4 regularly. The answers you are getting are possibly not as on-target as you would like.
2. There are likely multiple reasons for playing a known inferior move. Boredom, variety, "what the hell" (Doc Brown in Back to the Future), etc., including your "trolling". Answers like these can only be known to the individual who makes that choice, not to others who are left to theorize about it.

It seems to me your original question was entirely rhetorical, you have already made up your mind the only "reasonable" answer is "trolling". If that's the case, then who is the troll now?

For those of you who support 2. Bc4 why didn't you respond to the master's comment? Reading his comment to say white has equality may be a bit generous, Just thinking about blacks plan here gives me the impression that black should be slightly better.

by that argument you could justify playing 1. f3

I try to be open minded as far as opening ideas go. My issue isn't so much that people want to play 3. Bc4. People can play what they like. That doesn't bother me. What bothers me is that somebody makes an intelligent comment about why the move might not be so great and doesn't even get a response from those who favor 2. Bc4. I think I've had enough of this. Following this thread is probably a waste of my time, so I'm going to unfollow this thread. I hope everyone has a happy thanksgiving!

I showed two games in this thread where black gets what he wanted (e6+d5 achieved in both games, against 2.Bc4).

In both games, black ended up worse.

So it might be worth pondering whether or not e6+d5 does, in fact, give black the easy equality that he thinks it does. Or if, perhaps, chess is sometimes ... more of a struggle than that.

One could argue that, by playing e6+d5, black has hampered the development of his own queen bishop. Which diagonal will it enjoy at this point? The e6 pawn impedes it. So does the d5 pawn. Perhaps it has a lonely future on a6?

If black wishes to develop his queen bishop unfettered, in the future, along one of the strongest diagonals (c8 diagonal, or the b7 diagonal), then he will have to use a tempo to either: move e6 again, or to move d5 again. In which case, we could argue that any tempo he "wins" from kicking white's c4 bishop will then be returned to white, evening it out again.

We can see examples of this in the Ruy Lopez: white develops his king bishop and allows it to get kicked around the board for several moves.

Black might ask, "Why on earth would white play his bishop to b5, if he's just going to let black kick it all around the board?"

Similar arguments and ideas. Sometimes having a bishop kicked around doesn't automatically make that bishop placement a bad one.

I agree that the bishop on c4 does not seem ideally placed on move 2, against the Sicilian (it makes far more sense to put it there in the Italian, for example, as others have pointed out). But Black has already committed his own development "sin" on move 1: playing the pawn to c5, instead of developing a piece, or instead of moving a central pawn.

And so on and on it goes, with chess: both sides arguing against each other's moves. The only real answer can be found in the outcomes of the games themselves.

At lower elo, I can almost certainly say that anyone playing Bc4 has no clue how to play against the sicilian. Generally, e6 and normal play gives black a good position.

I seriously doubt, however, that anyone above 15-1600 plays Bc4 simply because they have no idea what else to play. It is a deliberate attempt to avoid theory.

As to the playability of the opening, I have won the majority of my games against Bc4, simply because I think black has very easy opening and middlegame plans. While it is not optimal, Bc4 is in no way inherently bad. The only problem is giving black a tempo with d5, which is relatively minor. It does not weaken any squares, nor does it compromise white's development. Certainly playable.

@84

"The only problem is giving black a tempo with d5"
++ That is not true: white gives a tempo with d5, but gains a tempo with e4 in 1 move and thus reaches a Nimzovich Indian Defence reversed with an extra tempo.

I wouldn't know off the top of my head, unfortunately. I play 2. Nf3 with no exceptions and then only offbeat variations depending on whether Black plays O'Kelly (a6), Katamilov (b6), Old (Nc6), Traditional (d6), French (e6), or Hyperaccelerated Dragon (g6). I also don't play the Sicilian as Black.
After a bit of research, the Bowdler Attack certainly looks interesting. If Black plays 2... e6, either to chase or ignore the bishop, 3. d4! immediately throws the center into disarray, and after all the fallout, the position looks to be in White's favor. If Black instead plays 2... Nc6, anticipating 3. d4, 3. Nf3 renews the threat of d4. After 3... e6 from Black, White can choose to play an Open Sicilian with d4 immediately, a Closed Sicilian with Nc3, or castle short and wait. If instead 3... Nf6 is played, white has all those options and more. 4. e5 is forcing and therefore the best move, as after 4... Ng4 5. Qe2, Black has to quickly decide what type of game will be played. If 5... Qc7 attacking the pawn, 6. Bxf7+ Kxf7 7. Qc4+ Ke8/e6 8. Qxg4, Black has lost castling rights and is slightly underdeveloped compared to White.  If 5... e6, stopping Bxf7+, 6. h3 Nh6 7. d4 cxd4 8. Bxh6 gxh6 and Black's king will be forced to stay either in the center or castle long, with doubled pawns on the h-file stopping both short castling and reducing the effectiveness of fianchettoing the DSB in this position. If 5... f6 with ideas of attacking the pawn and stopping the threat of losing a pawn to Bxf7+, 6. exf6 Nfx6 7. 0-0 and White is castled and half developed with the semi-open e-file, while Black is heavily underdeveloped with the semi-open f-file long term.
5... f6 is probably Black's best option in this position, as if both sides are able to complete development, the position is very even.
1. e4 c5 2. Bc4 Nc6 3. Nf3 Nf6 4. e5 Ng4 5. Qe2 f6 6. exf6 Nfx6 7. 0-0 as the best example of how to equalize from both sides.
1. e4 c5 2. Bc4 e6 3. d4 d5 4. exd5 exd5 5. Bb5+ Nc6 7. Nf3 Nf6 8. 0-0 (Be7/Bd6 9. dxc5 Bxc5 10. Nc3 0-0) as an example of the Open Sicilian version of the Bowdler Attack. If instead 8... Be6, 9. Nbd2 is best, with plans of going to Nb3. The game progresses from opening theory to variable middlegames here. I'd recommend the Bowdler Attack if you like sideline Open Sicilians and not mainlines, if you want to begin learning Sicilian theory but are daunted by the complexity, or if you just like offbeat openings in general. It might not be AS viable as other Sicilian variations, but it is still a viable variation.

This is sound logic... until you factor in human fallibility. Playing worse variations is usually a bad idea against a prepared opponent. Against a GM, for example, I could play an obscure Nimzo-Larsen Reverse English line and they'd still be well-prepared most likely, if not from memorization, than from experience. However, until we reach extremely high-rated titled players, this is not the case. Most likely, even experienced club, online, or titled players who play mainly or exclusively the Sicilian will still have only played the Bowdler a few times. Certainly not enough to get a feel for the middlegame and endgames. They might know a few (or even all, depending on experience, rating, and prep) moves of opening theory, but imagine a game in which White tried to play a mainline Open Sicilian. In this theoretical game, Black would have the upper hand immediately. More memorized theory, smooth control of the preferred middlegame, and a practiced endgame. White would have very, very little chance of winning this game, and Black would likely win rather than draw. In a Bowdler Attack, Black is suddenly as inexperienced as White, if not more so. The odds are much more even if neither side has a distinct advantage.

Coming back to a more broad sense, the reasons for suboptimal play vary: experience, playstyle, misinformation, personal enjoyment, knowledge about your opponent, mistakes, and more all play a part. At the end of the day, however, playing optimal openings only works if both you and your opponent play perfectly.

I will say, in blitz, I usually rejoice against the bowdler — my preferred variation of the Sicilian lends itself to best play against this opening

In classical, I try to just be solid, as the plans in my position are now stronger than those of my opponent. It’ll be a game, but I’ll be the one pushing for a win.

Your idea of most players not seeing the bowdler would be true for those who only play good opponents, but who among us hasn’t seen it in blitz at an early level? It’s prevalent even in classical sometimes

I would say maybe players who do very well with the bishops opening would play the bowdler and try those same ideas? Seems a bit inefficient, but a reason nonetheless.

Gata Kamsky (a strong grandmaster) plays it via transposition (playing Nc3 first, before Bc4).

Another one:

It makes sense that Kamsky likes putting his bishop on c4, sometimes followed by d3.

Because he's also a fan of this structure, too:

Bowdler attack is an innacuracy not a bad move