The Milgram experiment. We often listen to authoritative figures and do things we're uncomfortable doing, for what we hope will be result in a better good.
For example, I don't think there's one parent who didn't feel terrible having to see their child go through the pain of chemotherapy, but they did/do go ahead with it regardless. They put their trust in doctors in that the pain is necessary to help get rid of the child's cancer.
Can't that argument be made for the teachers in the Milgram experiment, where the teachers didn't blindly choose to hurt the subjects, but rather, they assumed that the study they were part of was done in the hopes of positive results which would be for the public's benefit (including that of the person getting zapped)?