He's that sarcastic guy who is always taking little jabs at people. Unfortunately the zombie apocalypse killed everyone's sense of humor and they have no idea how to react anymore. In the real world, you just deal with that guy and ignore most of what he says. You really want to punch the guy, but that would never fly. In the Walking Dead world, with all the heightened tension, that "don't punch him" filter is completely gone. Ultimately, you wind up shooting him.