I don't recall the leadup to that play, and the refs weren't flagging anything that wasn't that blatant up to that point, but if the db makes contact playing the ball, then that's typically allowed anyway. He came away with the pick, so it's not like he wasn't playing the ball.
I've stated numerous times that the first Bills PI was the one I'd argue went against what they'd done all game to that point, but since the roughing the passer also occurred on that play, it was still going to be a first down and set up the rest. The 2nd PI had to be called. Dude was beat and tackled the receiver to prevent the game winning TD. Tackling a guy who beats you is a penalty in every sport, and leads to a penalty shot/kick in a few of them.
