Those are all interesting... Kimmel and Fallon were both doing impressions of specific black guys. I don't remember the Karl Malone skit but would it even make sense to do the impressions in costume but not the makeup? You know would Fallon was acting like Rock because he does a pretty good job with it but being white yet with the facial hair and look would be really weird.
Silverman was straight up mocking blackface and the absurdity of it by playing a dip shit that thinks it's ok.
Stern did his skit with Sherman Hemsley and Robin which was a parody of Ted Danson wearing blackface when roasting his wife/girlfriend, Whoopi Goldberg, while wearing it.
Out of context they're all pretty crappy but if you're mocking dipshits for being dipshits is it that bad? Shit changes.
I don't remember Kimmel or Fallon using their color as a way to make fun of Rock or Malone. They didn't give them over the top features that could be negative.
Bad taste, sure. Stern has even said that he was nuts and would do anything to make fun of people and get attention 30 years ago and that he owns it, that there's probably a ton more out there that's even more outrageous, but that he wouldn't do it today because he knows it's wrong now.
Not my place to be the judge of things but I think that's what we want, right? Own mistakes. Admit that they're mistakes in retrospect and that you've grown and would choose differently today.