Really, this is one of those stories where most of the main actors come across poorly.
Will Smith acted poorly, letting a mean joke disrupt an entire night and there's little excuse for attacking someone.
Chris Rock acted poorly by making a mean joke at Jada Smith's expense.
I'm not really interested in protecting either man. However, we do need to set some rules that you're not allowed to assault someone because they're being a dick.
On the other hand, don't be a dick. Not all jokes need to be made, and it's okay to temper a joke. Comedians spend a little too much time thinking that every joke that's funny is necessary, and must be told.
I wonder how much bad blood there was already. The joke was mean, but I'm still shocked at Smith's reaction. Has he always been a hothead, or has something changed?