Will Smith shouldn't have slapped him, for several reasons.
1. He was laughing at the joke, and only went up to slap him when he saw Jada wasn't happy.
2. It was the tamest joke I've heard anyone make about someone.
3. It's a fucking joke.
4. The whole point of Chris Rock being there was to make jokes like this.
5. Jada cucked Will so fucking hard, and hates him, and shits on him 24/7, but Will is the biggest simp, and that's why he did it.
6. Jada has incredibly mild alopecia, and chose to shave her head. She also had the option of what over half of black women do, and wear a goddamn wig, but she chose to be bald, so if someone makes a joke about it, then that's that.
7. It's the fucking Oscars. He's just shown how absolutely low class he is by being unable to handle himself, and I wish that security would have taken him down and thrown him out after that, but of course that didn't happen.
If my wife had alopecia and someone made a joke that referenced her bald head, I'd first check to see if she minded, and if she did, then I'd just talk to the person that made the joke and say that she felt uncomfortable about the joke as it's something she's insecure about, not just smack the guy.