For some odd reason, multiplayer shooters bring out the worst in some people. You'll come across racist assholes, arrogant scumbags, cheaters and even boosters.
No matter how much you hate them, the people mentioned above are almost always part of the online community of a multiplayer FPS game and in particular -- Call of Duty games. For Black Ops 2, it's no different. I've come across people who were abusive, racists and even those who cheated their way to good stats (boosters).