No. It's one of my principles. I don't support any artist who claims to be a Nazi, or National Socialist, or whatever. And if I find out I have been without knowing (like the OP mentioning Magma) my support is withdrawn. I can support people who I disagree with politically-it's an occupational hazard with my reading of technothrillers and military science fiction unless they go so far beyond the pale that I can't stomach it (hello, Orson Scott Card and Ted Nugent) but I draw the line at supporting someone who believes in a political movement that caused a world war and one of the most horrific acts of ethnic cleansing in history.
And yes, I can make a distinction about Communism. However if someone plays in a band and idolizes Joseph Stalin, right out the door goes their music.