Apparently Jada's been getting roasted on social media for some time; it's hard to believe that Rock didn't know that. I also understand Rock trashed her at the 2016 Oscars. And in 2009 he produced a movie about Black hair, and all the issues surrounding it. He should have known it would be hurtful. To quote myself above,
"It's just a joke" is generally ... defensiveness for when you are rightly called out for being an asshole.
Also, the question of whether behaviour is bad, as opposed to illegal, is incredibly culturally specific. I'm not an American Black man, so I can't comment on whether Rock's joke or Smith's reaction was appropriate in American Black culture (although I might speculate on how one handles disputes in a culture where one can't rely on public authorities; or on the realistic ability of American Black women to defend themselves given their extremely low social status, tropes around angry Black women, and last week's shameless treatment of an American Black woman being considered for high office).
However, to the extent that Smith wants to market himself to a left or centerist white American audience, and to the extent that Hollywood doesn't want to alienate that audience, he may have done himself some damage. We will see.
From my cultural perspective, neither behaved well, although Smith acted under emotional stress (seeing your wife hurting is upsetting even if you didn't anticipate that she would be -
@Osrnoob you are totally out to lunch on this), and Rock acted while under no known emotional stress and apparently in control of his faculties. Combine that with the fact that a man slapping (as opposed to punching) a man is really intending to humiliate, not to injure, and my sympathies lie with Smith. I might not have slapped Rock, but I sure would have wanted to.