It was obviously a joke to me.
Somebody on another forum made a joke about Jada Pinkett Smith along the lines of Chris Rock's joke. I personally thought it was offensive, as did at least 1 of the mods, because it was a joke about a person with a disease/condition they had no control over. Was the joke taken down? No, because a majority of the mods didn't find it offensive. Was Chris Rock's joke offensive in his mind? No, because he didn't know about her condition. I believe he has stated he wouldn't have said it if he did. Was Will Smith's slap wrong? Yes, not only because he shouldn't have put his hands on another person, but also because he laughed and waited until he got the "look" from his wife and realized he was in deep doodoo for laughing; thus, his over reaction.
I guess offensive has become like porn, you'll know it when you see it, and I don't see it in the doers and takers joke.