I honestly don't see anything wrong with the joke - "GI Jane II, can't wait to see it." It is a joke about her and her bald head, which every person in the audience was thinking about. But it wasn't cruel. Cruel would've been, "Damn, Jada! You look like you're in an entanglement with Larry David!" And that might've deserved a slap. But Rock's joke about GI Jane was all positive, just light-hearted ribbing to someone you care about. Unless there was something else that I missed.
So Chris isn't allowed to make a joke about a beautiful bald woman? She could've worn a wig or hat if she was that sensitive about it, but chose to come with the bald look. She owned it and she looked great. The joke only expressed approval of her and her look. The over-reaction showed Will to be a self-centered attention hog and an asshole. He may be pussy-whipped but he's still responsible for his actions.
The fact that so many people think that was an inappropriate joke saddens me. I think it was perfect. lol. If she had just stood up and struck a muscular pose she would've been the Queen of the Oscars. Chris Rock would've said, "Damn, Will Smith you are one lucky man! I guess that's gonna become the new look." The baldness actually draws attention to her beauty and makes her even more striking, no pun intended. It's like beautiful flat chested women that somehow look even more feminine. The lack of one thing enhances the other.