Good points. Everything about Xander's character boils down to his homelife: the bad temper, the sexist jokes, the mean spirited streak, the way he could never get his point across without yelling.

It's also telling that we've never seen Xander drunk. Yes, there was that period after leaving Anya at the altar when he started drinking more often than he should, but he never got to the point of being drunk the way his friends and other characters did. It seemed like he'd always been careful with the amount of alcohol he'd drink.