I don't think it's a question of whether their achievements are nullified, but as you mention, how to weight the opinions of various people. Personally, I think both a Turing award for technical achievement and a view that humanity ought to be replaced are relevant in evaluating someone's opinions on AI policy, and we shouldn't forget the latter because of the former.

(Also, this isn't about Sutton's personal life - that's a pretty bad strawman.)