I wrote the other day about whether the failings of someone's personal life (or their rebarbative views) should act as some sort of prohibition on the study or use of their work. I cited Einstein and Kant, but there are countless others; Mel Gibson and Arthur Koestler come immediately to mind.
There are obviously no set rules for this – much as some would wish it – and there are a lot of factors involved. Helpfully, the Economist feature: How much should artists’ personal lives affect how we treat their work? sheds some light on the factors (if not the rules).
This is part of their Open Future initiative which I commend to you.