What's up with fps vs. fps infighting?

I just don't get it. People who play this game talk shit on people who play that game. People shit on Call of Duty the most, why does it got to get so much flak. I never understood people hating on a certain game, especially when people say that one game is inferior to another. I play CoD, I play Battlefield, I play Halo and TF2 and enjoy each equally. How do you feel about people infighting between games?

>>8 It's a common thing to see on the internet and it happens often. I wasn't intending to argue with people about games, I made this to see how other people felt about all the arguing.  Who cares, I don't fuckin know.