Full disclosure - I'm a white woman.
I think there was a lot of shock that prevented anyone from doing anything immediately - you just don't expect that and people don't know how to react.
I don't think Chris Rock would have said something like that about a white man's wife (I think that type of automatic self-censorship, especially in black men, is so ingrained it just would not have happened).
I think if Chris Rock had said he wanted Will Smith removed they would have. They asked him and he said "no" (at least that was my understanding).
I think if a white male star had slapped Chris Rock that it would have very much depended on the stature of the white star (how much power they were perceived to have in the academy and in the industry). The lower his status, the higher the likelihood of removal. However, I still think they would have asked Chris Rock.
I think that if a white man had slapped Chris Rock and they had removed him, his removal and an apology would have likely been enough without a 10 year ban but, again, the stature of the white man would have made a huge difference.
My take on the whole thing is basically that one male did a violent sexist thing to another male in response to a violent sexist thing the other male had done. I don't think the academy gives a f**k about women and especially about black women/WOC and had Will Smith merely yelled at Chris Rock from the sidelines they still would have slapped him on the wrist because saying shit about women is perfectly fine but disrupting their big narcissistic awards show is a big no-no.
Finally, I think DU is like the real world - there are racists and misogynists in the Democratic party and they are here, too. There are less of them than in the country on average and exponentially less of them than on the right but they are here, never-the-less.