Let's say there's a girl called Alice and a guy called Bob.

Bob is always nothing but nice to Alice and she rewards him for it by kicking him in the balls.

Bob is understandably upset and becomes bitter at Alice for kicking him in the balls and stops being as nice to her as he was before.

Alice then sees how Bob's treatment of her has changed and takes it as "proof" that he was never actually nice to her in the first place and was only pretending to be. Alice then posts the interaction on /r/niceguys and gets thousands of upvotes.

This is unjust to the point of absurdity. What was Bob supposed to do, continue being nice to a woman who just kicked him in the balls?