My view on this is less dogmatic - some may call it inconsistent.
I enjoy Megadeth and Iced Earth immensely, even though I think Dave Mustaine and Jon Schaffer are nutcases. I do not support the political agenda they subscribe to, but in both cases, I can sort of look over it. Mustaine has always been a freak who spat out the weirdest shit imaginable. I've always felt it was more about a need for attention and an unrealistic sense for self-importance, and for that matter, I've always kind of liked him for all of this. He's just very entertaining to watch, and his music is always more or less the stuff that 16 year olds think of as cool.
Things are a bit different with Jon Schaffer. I stopped following what he does when he started with his Sons of Liberty rampage, and when I heard
Dystopia, I really lost all interest in what he and Iced Earth are doing. Part of that is certainly due to Schaffer's behaviour, but the other part is that
Dystopia really was one of the worst albums I had ever heard. If that is the kind of music the band will be doing in the future, my once very intense love affair with Iced Earth is over. Nevertheless, I still enjoy their classic albums a lot and won't stop listening to them.
The way I see it, Schaffer and Mustaine are harmless people who think they have it all figured out and will talk a lot about their views - but it's always the music that is in the foreground, and unless they write the next
Horst Wessel-Lied, I can easily separate things.
Then, there really are people who use their music as a platform to propagate their ideas. The lyrical contents of black metal bands such as Dark Funeral or Dissection are sometimes very questionable, if not completely objectionable. Sometimes I think it is mere provocation, but sometimes I think there is some genuine evil inside. This is the case with Varg Vikernes and Burzum, for instance. Musically, Burzum is really incredible, but I have never managed to separate the music from the person who made it - a murderer and arsonist, who developed a sophisticated nazi ideology in prison. Maybe it's just that this is such an extreme case, and I simply fucking hate nazis that I am singling it out.