I feel compelled to state that anti-Semitism is a particularly sensitive question for me, one has a tendency to cause some horrible moral dilemmas.
That being said, since I am not inclined to idealize men and since hero worshipping has always made me uncomfortbale, I usually manage to make a distinction between the art and the artist, especially more so since musicians in particular tend to be a very confused bunch of people who often can't really think clearly, and a lot of them would probably benefit from a little slap in the back of their pretty little head every now and then to bring them back to their senses.
So I can despise Schumann the anti-Semite but admire his genius as a composer.
Or the work of Jimmy Page, one of my favorite rock musician, while condemning him as the complete moron that he was for his little stunt in the Stortrooper uniform.
Same for Bowie, although it is a bit more touchy considering that in his case, it wasn't just one isolated stunt.
Not Wagner though. Him I hate through and through.