H. P. Lovecraft is a good example from literature. He was profoundly racist, even beyond the cultural norms of his time. However, as he has long since passed away buying and amplifying his works do not further his views and causes.
A modern counterexample would be J. K. Rowling. Where supporting her works and properties does directly contribute to furthering her prejudices in a very real way.
i'd rephrase that. it does not support the artist to allow him to continue spreading his views and causes, but it still draws attention to him, and potentially lets people learn about it. even this discussion here. i would not have known about lovecrafts or rowlings views if it weren't for reading about it on hackernews some time ago.
however an even more important concern is how much of these views are woven into the stories. as such it is important to at least be aware. i have ignored harry potter until now but my kids are getting interested, and so i am keeping a close eye on what they are watching for that reason.