This game is a classic example of a glitch in the rating system. You've got the campaign mode, which should be rated M, and is, and then you've got this excellent multiplayer with very little blood and no cursing at all, but you, the insensitive parent, go, "Oops, this game is rated M, and even though I could just get the game for my teen kid and let them play the multiplayer, which is still a great experience in and of itself, I'm just going to let the rating speak for the whole game without considering that it might be a very nuanced game." And for those of you who say, "But people curse in the chat!", I have three things to say.
-Player language is not rated by the ESRB.
-Or, just don't use a mic.