Let me add somethings of importance then: one can be thief and/or murderer (like e.g. Caravaggio, François Villon, Burroughs, Jean Genet, Cellini, etc.) and still be a great writer, poet, painter, sculptor, etc.

>I will not, however, accept that the contributions either justify or excuse harmful behavior.

Could be the worse, the harmful behavior could inform the contributions.

Good people can still make great art (Bach for one), but they don't make great art of the kind bad people make, nor do they have the same access as bad people to express those impulses and that side of humanity.