My son had alopecia areata when he was 10. He was made fun of and bullied in school over it. One day, at his soccer game a parent called him baldy from the sidelines and I heard it.
Can't say I reacted much differently than Will Smith. Being a coach, it was a bad look. But every player on my team thanked me and a slew of parents gave me "Well done" pats on the back.
Alopecia is a tough disease to handle for those that should have full heads of hair, kids and women, especially. Whoever allowed that joke to be included should be fired. If Rock improvised it, don't bring him back.
As for Will, as with me, not a good look, but I completely understand his passion, rage and what he did and why.