You can reconcile what needs reconciling by recognizing that moral responsibility isn't an either-or kind of thing. In most situations, moral responsibility is shared by multiple people or parties, and it's usually not so easy to figure out who's responsible for how much of what.

Say a kid grows up and turns into a public mass murderer. Goes and shoots up a night club. Turns out he was bullied as a kid. Turns out his teacher didn't handle the situation right. Turns out the principal when he found out about the situation only made it worse. Turns out the kid was abused by his dad too, which is what primed him to be the victim of the bully. And his mom was a meth addict. Also, turns out his uncle forgot to lock up his gun cabinet, allowing the now extremely disturbed 17 yr old to carry out his massacre. Bully, teacher, principal, dad, mom, uncle, killer... can we throw in the bully's parents too? How about the bully's parents' parents for not raising the bully's parents right? And so on. Ultimately, the young man is the decision maker, the agent acting on free will. He bears most of the blame. But of course he had help. The full portrait of moral responsibility is very messy and complicated, and hard to sort out.

Likewise with all the situations you mentioned. Art has an impact. Artists always bear some responsibility for that impact. It's rarely the dominant factor in anything, because for better or worse, art does not change the world. It's relatively inert.