That the joke was "tame" isn't for us to decide considering that it clearly didn't land well with its subject (Jada Smith):
We know about how it affected Will, but how do you
know the effect on Jada?
Nonetheless, it is indeed for us to all consider how
appropriate his response to the level of insult intended
& inferred. This is not merely of social concern, but
also public policy, particularly when it results in assault.
Smith was wrong to become physical, but Chris Rock's joke was inappropriate as well. The idea that comedians should be able to say whatever they want without second thought is outdated and mistaken, and Chris Rock and some other older comedians from a less socially aware period are now increasingly finding this out.
Comedy is pain, & inappropriate jokes are the best.
Woe unto a society that can no longer tolerate a
Chris Rock, Ricky Gervais, Triumph, Joel McHale,
The Dice Man, or Lenny Bruce.