I really, really, really hope this is satire.
They're being aggressive with you for not liking CoD. Judging by the tone of your OP, you probably said something like "Why are you playing CoD, you mindless sheeple. You should play this other game, because I'm better than you." In which case, they would be justified in being aggressive towards you.
Sure, your one friend was a dumbass. The again, it sounds like you were talking over PSN/Live. It's entirely possible he was just exasperated by the fact he had no one to play Black Ops with and sent you a message that was easy to misinterpret. Typing with a controller is hard, so people tend to type whatever makes some sense and send it, rather than making sure the message is clear.
Regardless, liking a game does not make you any kind of sheep. For one thing, sheep are actually quite intelligent. For another, despite your superior attitude, you aren't any better than your friend. Congratulations, you noticed human beings tend to act in certain ways. So has everybody else. You're just as much of a "sheep" as your friend. You just act out of the norm enough to convince yourself you're different.
At least your friend is content. You've managed to convince yourself your different, without being different. Your friend is aware of where he is in life, and has learned to accept it.