I don't agree with almost anything Morrissey says, but it wouldn't stop me going to see him again, as he's a genius, people should be able to separate politics from music, unless of course the musician is in the KKK or an actual Neo Nazi.
It's a really difficult issue. Ultimately free speech is incredibly important but then there's a balance between that and giving people a platform to be hateful, spout rhetoric and encourage such behaviour in others. Also venues should have a right to decide whether they want to permit someone to play there. I'd feel uncomfortable if an arts centre was forced to allow someone to go along and deliver hate speech to a mob of pricks under the banner of free speech.
Morrissey and Roger Waters are both complicated. I'd have absolutely no interest in seeing Morrissey now as I think he's become a far right bellend. I'd still listen to a Smiths song at home as I feel that's different - that's the work of a group of people from a different time, before Morrissey seemed increasingly like a wrong'un. I wouldn't feel remotely comfortable giving him money to see him perform and listen to him spout shit at me.
This Roger Waters thing seems to be predicated on a misunderstanding on the purpose of his outfit. The whole point of the Wall album and associated performances is to decry war and fascism, though I appreciate it would look weird if you've never seen it before and Germany has strict laws a out that sort of thing.
That being said, whilst I saw the Wall show he did at the O2 a decade ago, I wouldnt go and see him now after all of his bullshit about Ukraine and Russia. I think he's using his platform to deliver dangerous misinformation and I wouldn't want to support that. Still adore Pink Floyd and listen to their albums though. Maybe that makes me a hypocrite
Ultimately it's up to fans to make a decision on the gravity of what artists do (or are accused of doing). I still listen to Arcade Fire now, they're one of my favourite bands ever, but I wasn't comfortable getting tickets to their recent tour after the allegations against Win Butler. And there are musicians who've behaved reprehensibly. I'd be very surprised if many people still listen to Lostprophets any more and I can't really see how you could separate music and musician there.
It's a grey area isn't it. Where does an artist cross the line - is it as you say if they declare themselves a KKK supporter or a neo Nazi, or someone before that? Ultimately it's up to individual consciouses what they're comfortable with.