Not much. When someone does something, and that same person has a goal that you disapprove of, you have to think about two things: the influence of that deed on that naughty goal, and and the influence of that deed on your goals.

Note that those two things can be conflated in one: if you disapprove some goal, then a part of your goal is to make that not happen. So in the end, the only thing that matters is the influence of the deed on your goals, period.

Now the deed cannot be evaluated alone. You need to know how it interacts with the world. And the first place to look at is the other deeds of the same person. (There lies the validity of Ad Hominem arguments.) However it's not the only place to look at.

For instance, if a Paper-Clip-Maniac wants to solve the Friendly AI problem, you probably don't want that problem solved: it could fill the universe with paper clips, wiping out all sentient life in the process. Now, say you're a transhumanist, and you want to cure Death. Solving the FAI problem suddenly look much better. It may even be worth the risk induced by that Paper-Clip-Maniac.