Transhuman: I know you would never make fun of a woman's hair loss issues but let's say you find yourself in this situation, you are hosting the oscars, William Smith has just slapped you and is yelling "keep my wife's name out yo mouth"
how do you recover and play this off
To be honest I hate Chris Rock's joke enough that I would never be in the position of telling it. Not because I find it offensive, I just think it's a lazy easy joke. I can think of a few jokes that make fun of her baldness that are funnier. "And Will Smith is with his wife tonight Jada, who suffers from alopecia. Y'know at one point Will considered shaving his head in solidarity, but in the end he decided it wouldn't be fair to all the other women he's seeing". That way it still mentions her baldness but instead it's about the even more notable thing, their very public marriage (it's public but you still have to be a 9.5 or above). Plus it doesn't rely on the audience having seen Gi Jane. I find reference jokes lazy. This person looks like 'X' other person? That's one of the first things you learn not to do. You have to dress it up a little. "I'm sorry Jada, I just got off the phone with James Gunn. They decided to go in a different direction..." I suppose that's still a reference joke, but it feels a bit funnier. Hide the punchline a bit, add some suspense, reference a movie that came out this century, etc. Strictly speaking, funnier.
If I were recovering in the moment I would probably say: "I'm sorry Will. We all make mistakes. Remember After Earth". Which I don't think is particularly funny because reference jokes I find boring but if you have no time to spare like I said, they're easy.