Even on Halo and Call of Duty's most recent incarnations (and going far back to some of the earliest entries in their respective franchises), it's a rarity to find someone that's actually a douchebag. Keep in mind that this is Xbox Live we're talking about, which seems to have a reputation for being an eldritch abomination of profanity and racial slurs. Hell, the minor trash talk my bros and I toss back and forth during splitscreen is more intense than what I usually hear online.
Most often, I'll just hear mild anger from a team mate if he feels he was killed in a bullshitty way. There's still teabagging in Halo, but usually only when someone I've been dominating gets revenge, which is totally understandable, if not completely justified. Long story short, I've encountered very few antagonistic players, and the handful I've encountered in my many years of playing are mightily overshadowed by plethora of friendly, cooperative players I've fought alongside.