What computer says that? It is Stockfish's prefered move (-5.29)
Why can't the bishop take the pawn?

What computer says that? It is Stockfish's prefered move (-5.29)
chess.com analysis says that. I personally like Bxb2.

hmm, at 24 ply it likes Nd7 better now, but not by much.
Bxb2, Nd7, Nc6 and b5 all score about the same

Actually, 3. Rxb7 is probably a great move! Followed by the knight jumping all over blacks camp. Maybe this is why 1...Bxb2 isn't so hot.

After 1...Bxb2 2.Qb4 isn't black in serious trouble? e.g. 2...Bf6 3.Qxb7 looks deadly
I think Black can toss in ...b5

After 1...Bxb2 2.Qb4 isn't black in serious trouble? e.g. 2...Bf6 3.Qxb7 looks deadly
I think Black can toss in ...b5
Sure, but White keeps a large advantage after 3. Bxb5 or 3. Bb3 Bf6 4. Nxf6+ Qxf6 5. Rxd6
Also, 1...Bxb2 2. c3 Ba3 3. f6 is another way to prove an advantage for White.

So tc, do you see why Bxb2 is bad now?
Yes, makes perfect sense now. I was actually playing white in this position. Taking a step back the diagram shows the position with white to move. I was paranoid about the bishop taking that pawn. And so I took it out. I just wanted to learn why I was so paranoid about nothing because at the time I didnt see the great position for white after Bxb2. Now I see it.
The computer says the Black bishop should not take the white pawn on b2. I can't for the life of me figure out what's so bad about taking that pawn? So what is blacks best move?
I whole heartedly agree with the computer after looking at the diagram for only 2 seconds, and I'm rated 1400. This is a very classic, basic chess principle that Bruce Pandolfini has taught 100 times.
1. Black need not fear NxB since the Night is very strong where it is at.
2. White will respond to BxP with Rb1. The bishop will then have to retreat to safety, and the rook will take on b7, followed by Rfb1, Rc7, R1b7. You do NOT want doubled rooks or even one enemy rook on your second rank, and you certainly will not be up a pawn after the exchange. Granted you did isolate some pawns, but at the expense of giving white a file to invade.
Doubled rooks combined on your second rank, especially with a night purched safely on d5, spells certain doom for black.
hmm, at 24 ply it likes Nd7 better now, but not by much.
Bxb2, Nd7, Nc6 and b5 all score about the same
Nd7 is a pretty good move. It connects the back rank, allows the aRook to come to b8, allows the knight to go to b6 to challenge the d5 knight, allows it to go to the c5 purch, and guards the f6 bishop.
b5, prevents Rxb7, and is preparing for Bxb2. It also gains time by chasing away the c4 bishop, but can be challanged with a4 soon after.
After 1...Bxb2 2.Qb4 isn't black in serious trouble? e.g. 2...Bf6 3.Qxb7 looks deadly
Qxb7 is not deadly at all. Nd7 connects rook and Queen on the back rank. The 7th still is compromized, though, but it is much easier for the black queen to challange another queen that it is for it to challenge a rook it would not want to trade with.
I've been looking at every poster's profile and have noticed a pattern: those with live chess ratings agree with the computer, whereas those with much higher turn based chess ratings tend to disagree with the computer.

After 1...Bxb2 2.Qb4 isn't black in serious trouble? e.g. 2...Bf6 3.Qxb7 looks deadly
Qxb7 is not deadly at all. Nd7 connects rook and Queen on the back rank. The 7th still is compromized, though, but it is much easier for the black queen to challange another queen that it is for it to challenge a rook it would not want to trade with.
I've been looking at every poster's profile and have noticed a pattern: those with live chess ratings agree with the computer, whereas those with much higher turn based chess ratings tend to disagree with the computer.
After 3...Nd7, 4. Nxf6+ is killer because of 4...Qxf6 5. Qxd7, 4...Nxf6 5. Bxf7+, and 4...gxf6 5. Rxd6 Re7 6. Rfd1.
Just realized I was missing a white rook in the diagram. LOL!! This might change some things.
The computer says the Black bishop should not take the white pawn on b2. I can't for the life of me figure out what's so bad about taking that pawn? So what is blacks best move?