After all, many academic subjects study unsavory aspects of human behavior. Political science, history, psychology, sociology, and literature are often concerned with aggression, obsessiveness, selfishness, and cruelty, not to mention lust, sloth, greed, envy, pride, wrath, and gluttony. But no one seems to fear that students in these other disciplines are on the fast track to becoming sociopaths. Why is economics supposed to be so uniquely corrupting?
I think that economics is singled out for opprobrium because of the way that it challenges the intention heuristic. The intention heuristic says that if the intentions of an act are selfless and well-meaning, then the act is good. If the intentions are self-interested, then it is not good.
The intention heuristic is what generates the veneration of non-profits. One can readily suppose that the intentions of a non-profit are better than those of a for-profit institution. Accordingly, it seems morally superior to work at a non-profit. However, once one drops the intention heuristic, the case for non-profits becomes much weaker.
I think that the ability to think beyond the intention heuristic is very important in social and political philosophy. However, there are many people who are heavily invested in the intention heuristic, and it is my hypothesis that such people are anxious to discredit economics.