Separating Man from Manuscript

I was having a cigar and listening to excerpts from Wagner's Ring cycle this evening (don't judge me!) and I began reflecting on how such a horrible man could write such beautiful music. But then I realized I was being unfair. Was Wagner really a horrible man? His antisemitism is a matter of public record. But as with most things, it was quite a bit more complicated than that. He had Jewish friends; he described one of those friendships as "one of the most beautiful friendships of my life." Few men—or women—are entirely good or entirely bad. Bad people can do good things and good people can do—and believe—bad things.
So where should one stand when it comes to literature? Must I not read another word of Lovecraft after being exposed to this poem ? Should Orson Scott Card's views on homosexuality prevent me from reading his books? What if I found out that an author whose work I enjoy is an unrepentant asshole? How do I—how does anyone—separate the man from the manuscript?
Yes, good people can believe what I, from my perspective, would consider bad things. But as long as that perspective is not overtly manifested in their artwork, is it still "ethical" for me to enjoy that work? Axl Rose seems to be a generally despicable human being, but in my mind "November Rain" will always stand as one of the greatest rock songs of the early 90s. Do I have to stop liking Manhattan and Chinatown because of Allen's and Polanski's inappropriate (and criminal, in the latter case) behavior with young women? I read a great deal of Victorian literature and racism and sexism are often on display.
Is there a certain line an artist must not cross before his or her work should be universally shunned? I really don't know. As with all things ethical, it is often situational. I may be able to overlook something another may not and vice versa. I think what a responsible person must do is acknowledge that all people are flawed in some way. We must acknowledge the uncomfortable positions some of the great artists of the past have held and understand that we are all products of the time and place in which we live. It cannot excuse everything but this understanding should help us to not let the ugly details of their lives detract from the good or beautiful things they may produce. So I will continue to listen to Wagner. I'll continue to read Lovecraft. And I'd like to know what you think about the issue. Leave a comment below if you'd like to chime in.
Before I close, I'd like to bring up one more aspect of this "separating man from manuscript" idea. If you are reading this, there is a good chance you follow writers on Facebook or Twitter. Social media has enabled readers to have unprecedented access to the people who are writing the books they enjoy. If a writer posted something that, to you, seemed racist/sexist/bigoted/what-have-you, how would it affect the way you buy and read their work?