If you know someone who loves painting and a mural needs to be painted on Saturday, is it really crazy to think it's less bad to ask them to paint the mural than it would be to ask someone who has no passion for it at all? The question is not "Would you prefer a world in which we ignored the differences in passion and decided to never exploit anyone at all?", the questions is "Which is worse?". It does not say anything at all about whether people think these things are OK. If I tell you killing one person is less bad than killing two, that doesn’t mean I think killing people is OK.
"Participants read about a Ph.D. student’s working relationship with their graduate advisor. Those who read a scenario in which the student was being exploited – verbally abused and given unreasonable deadlines – rated the student as likely to be more passionate than students who weren’t being exploited."
Isn't that true though? If there's an identical distribution of passion across advisors at the start of the program and passion is negatively correlated with deciding to drop out in response to an exploitative advisor, people with exploitative advisors are therefore likely to be (although may not individually be) more passionate. It's essentially just asking if passionate people are more likely to continue towards a goal even in an exploitative environment, and has nothing to do with whether that is a good thing.