THere's some jackass with a crying baby in this game. How the hell do I mute him?

Party chat.

Go to the recent players menu, go to the player's profile and mute him there.

@SkullcrusherMountain: If you hit start, there should be a button or option to mute people. It's a protip that pops up in the loading screens.

@Napalm said:

@SkullcrusherMountain: If you hit start, there should be a button or option to mute people. It's a protip that pops up in the loading screens.

@SkullcrusherMountain: Do this. If you want to mute a specific player or mute every stranger in the game (as in anyone that's not on your friends list/in your current party chat), press start and then X. Press start again (or it might be Back) to mute strangers and to mute one person, just highlight and press A and I'm sure the option is in there.