DH and I almost broke up once (long before we has kids) because he mentioned something about smacking our kids and I blew up at him We talked it out, and I ended up getting him to see my point of view on it. He was smacked (well, belted, really) and I wasn't.

One of the begrudging bits of respect I have for my dad is that he never ever hit us. We disagree in so many ways, but this is one we're on the same page about. If I see or hear someone hitting their kids when I'm out shopping, I have to restrain myself from retaliating on behalf of the kid...