Speed of Thought in Blitz?

So, many of us experience poor sportsmanship now and then on chess.com, and I'm sure most of us who play blitz have been accused at least once of cheating when we win a game. People get upset, tempers flare, etc.

But today I had someone accuse me of cheating through REALLY SPECIFIC evidence, and it's got me curious.

Basically: I played two games with this player. He won the first; asked for a rematch; I won the second. At which point he accused me of cheating. He added in that I was using the lag somehow to win both in position and on time.

You're welcome to review the game; we both made plenty of mistakes: https://www.chess.com/live/game/2150888891

BUT HERE'S THE SPECIFIC QUESTION:

My opponent said I must be cheating because I took a pawn en passant too fast. It's in move 48 in the game above: fxg3+; 1.2 seconds of black's clock spent on the move; I had the black pieces.

Now, I know I didn't cheat: we were both low on time and I was focusing on clearing his pieces so he had no shot at draw points on time. I was about to push g3, offering the pawn exchange, knowing if he pushed past I had the rook to chase down the pawn. Instead, he gave me an en-passant opening. I was focused on those squares; I took it.

I tried to argue that in the post-game squabble we got into, and he didn't buy it. He said no player "in the 1700s" (my rating was 1794 at the time, fwiw) could think of en passant that fast.

So that, I suppose, is my question: is 1.2 seconds enough time to react to a pawn push with en passant? I suppose my empirical answer is yes: after all, I did it. And looking over the game, lots of moves, even in complex positions, took less time than that. I suppose partly I'm feeling bewildered by the argument, and wondering if anyone takes it seriously, or if I should just shrug it off as unusually-specific sour grapes?

So how long do you think we need to be able to react quickly with good chess play, even not knowing what the opponent is doing? How long should an average bullet-game move take?

I don't see any reason a player wouldn't see or even anticipate en passant, as you did.  Personally sometimes I see it instantly, sometimes I do not.  I had a recent daily game where I made a move knowing that I could take en-passant if my opponent made what would otherwise be a good move.  The next day he made it and I briefly forgot about en passant and began asking myself why I didn't see the move - but it quickly came to me.  I had Black and the en passant was on the 15th move and put me a Pawn up - which I converted to a won game:

I don't understand the question. Of course you see an enpassant opportunity instantly. Is the question whether or not you SHOULD take it in 1.2 seconds? Because I have like 1100 and I autotake enpassants by default. He needs to stop his whining and you need to stop caring about whining people.

 I have had encounter with many players who seemed to be cheating but it doesn't bother me.simply block them from further playing with me..The game in question as per my opinion is black hasn't done  

 any cheating at least not at move 48 as alleged.I have lost games with Q and R and opponent only having a minor piece(time trouble).In one game my R in 2nd rank,King 8th rank,Q in 3 rd rank.Opponent

King alone was in 1st rank,he had no other pieces or pawns.gave check in 1st rank with queen and lost.

due to time out .My friends in admin.team asked to complain but I didn't because not bothered about a win or loss.