I don't know why people get worked up over it. The unbridled hatred, racism, bigorty, sexism, grammar wars, self-deprecation, fandom wars, and etc. that take place there are the stuff of legends.
I think you answered your own question.
I might have but you'd think people would realize that they're just baiting folks into useless arguments.
It's a difficult concept for some, but "unbridled hatred, racism, bigorty, sexism" done as a joke is still unbridled hatred, racism, bigorty, sexism on the page. Even if the commenter isn't actually hateful, a racist, bigot or sexist (but really, how do you know?) it's still out there just the same as if they did, and even worse you've got real hateful racists, bigots and sexists looking at your words and going "cool bro, it's nice to know somebody gets me". And seriously, when you've got those sorts of people looking at you approvingly, you've got to take a moment to wonder where your life went so wrong.
Other than "the poster gets off on it for whatever reason" and "dudes who don't personally have to deal with those issues in day to day life find it funny" there's no upside.