That's like saying that the long and short of the entire show has been, "Hey! Shit! Zombies! BANGBANGbang stabstabstab (some peoples dies)." While technically true, doesn't really capture the entirety of the situation. Might as well ask why anyone does anything. He feels that with the set of circumstances before him, he is justified in the actions he takes. He's probably always been a dick, just in more minor, socially acceptable ways. If he wasn't lying about that story with his wife, then sure it's sad. But it's gotta be in no way the whole picture. We don't know if he was an abusive husband, a drunk, a passive aggresive torturer. His job sucked? Maybe he sucked at it. Maybe he was a prick there, as well. Or maybe he was a deacon at church, and an all around good guy, who just fuckin snapped when the zombie apocalypse hit. I'm guessing that a lot of people aren't going to deal real well with that sort of thing if it ever happens. Mostly, it seems like everyone has been nitpicking the shit out of the show while they're clearly manuevering pieces for a big ending.