I understand, that is why a court of law will only accept evidence that leaves no doubt about someone having committed a crime. The court of public opinion has no such requirement though, and I don't think it should have. Often times it is exceedingly difficult to prove rape/SA, especially because many victims need time to eventually report the crime. That is because the victims face a lot of scrutinization (often times more than the accused person), which they obviously tend to avoid because it's such a traumatic event. So I think it's fair to judge someone accused of SA, because usually it's true even if the victim is unable to prove it.

That being said I also believe in separating the art from the artist, at least to a certain extent. If the music encourages SA, I wouldn't listen to it (regardless of accusations, really), but otherwise I won't let the things the artist (probably) did distract from the art. Hitler also did nice paintings, and I don't see why we shouldn't appreciate the paintings for what they are, even if the person who created them was obviously evil.