Can't say i know him personally but one thing i do know is that most people that act like the way you described are usually having issues with themselves and get some type of gratification from projecting their own insecurities upon others to take the attention away from themselves. There's a few on this site but they're all cowards and hide behind a keyboard.
i have encountered this vicious attacking cheese player who isn't really even very good (what Andrew Martin would call expertise at "caveman cheese") on this website and he just insults me non-stop while we were playing a game of cheese. His username is newengland7 in case that wasn't oblivious.
I am wondering if any body knows this person in real life and if he is this much of a jerk in the real world as well.