It sucks seeing the hate MLG gets here with no defense.
You guys have to realize there's a difference between the people who actually play MLG professionally and are sponsored and the kids who wish they did.
A good number of the pros can be jerks, of course, but for the most part they're good guys. All of Final Boss, for example, are extremely mature.
A while ago (early 2005) I had the fortune of getting matched with AYB Fonzi in Rumble Training or something. He's one of the better players on the MLG Circuit and he was nice as could be. We made small talk throughout the match and I wished him luck for the season and all of that. He won considerably, as expected, but he never trash talked or anything. He was just a nice guy.
And, on the whole, MLG is doing good things for videogames. The immature pricks are a huge downside to that, but fortunately Bungie's new and improved mute option will help with that.
EDIT: Wow, the hate got even worse as I typed that.