It's not a question of whether he should be profiting from his work, it's a question of whether people are OK with listening to a fucking pedophile singing sweet nothings into their ear holes. That song and many others could well have been recorded just hours before or after he fucking raped a defenseless at risk child.I haven't seen Joker so I don't have a horse in this race. I'm also from the UK, so I know full-well Gary Glitter is a monster.
That being said, If people convicted of crimes don't deserve to profit from their previous works, then that's a situation for the justice system to sort out - not filmmakers. As it stands, I'm pretty sure people convicted of crimes (however heinous) can still own and earn money from intellectual and physical property.
There might be an argument to be made that being convicted of a certain severity of crime should come with a forfeit of those rights, but again, that would be a world-changing judgment that would need to be made at the highest echelons of judicial review.
As we've seen many times already with other people who rape children, some people are apparently happy to continue listening to their work or watching their work.
I can't. It's vile. I don't care abiut the film one way or another.