Are there any studies on the ethical and moral presumptions in taking miscreants' money? Is it required to shun miscreants? Is it an approval of miscreant actions if the money is taken?

Is it that the miscreant may come back and say "this is why I do it, so I can give.."? Would a simple public disclaimer "we not only not condone, we vehemently oppose ..." at time of donation resolve this? What makes taking with a disclaimer hypocritical?

If you were dying of liver cancer, knowing a a new liver would save you, and a murderous dictator walked up and said, here is my matching liver, would you take it?