Jackson Pollock doesn't strike me as the world's nicest guy. Picasso either.
Being a creep doesn't disqualify one from being a great artist, no.
People who break the law should be prosecuted like anyone else. You can't take away what's already been done though. If they've already made art, or performed surgeries, tried cases, taught classes, etc., you can't erase it, but you can certainly take away their status or certificates to continue to practice. With artists, it's up to the people that have the work on their walls whether they still want it or can separate the art from the artist. There is no right answer. The artist can still paint from their jail cell, if given those benefits. Same goes with their "good/bad" views. It's up to the people who support them. You can't really jail people for their views, but you can be disgusted enough to think about it every time you see/listen to their art. Isn't that the audience's decision? It's not a black and white world.
I would like to think that the evil wrought by Hitler will not be forgotten... nor that of Stalin and Mao. Nero, Commodus, and Caracalla are still all known for their evil deeds. Napoleon, I think, is different. He had power thrust upon him as a result of the wars against the French by the allied European aristocracies that feared the revolutionary ideas of the French spreading. He never dreamed of an eradication of even his enemies but rather a unified Europe. Like the French Revolution itself with spiraled into the horror of the Reign of Terror, Napoleon's goals... which may have been noble in intention... resulted in endless death and suffering. I do think that humor has long been one of the prime weapons against tyranny and authoritarianism... but unfortunately, we have more than a few who fear change and the "other" and will whole-heartedly embrace authoritarianism.Ya, maybe we'll all just finally forget what Hitler did (and every other genocidal evil monster did) and we can all just have a good laugh, right? I think in some ways you might be right--that many many years after these monsters are dead, people do seem to forget, unless people that were directly affected are still among the living. Just like how people who were not directly affected by Hitler in modern times don't really care about what he did. It wasn't their family, why would they? Fewer and fewer people care. This is why history will just keep repeating itself.
I would never suggest that an artist is some sort of being that should be held above the law... but trying the human being for his or her crimes is not the same as vilifying the works of art. I would not see think of blaming the sons and daughters of a murderer or rapist for their father's crimes than I would think of blaming Tristan und Isolde for Wagner's antisemitic writings. I would also point out that in most instances, all humans are complex beings and cannot be defined as wholly good or bad.