It really is easier to get forgiveness than permission:

In 7 studies, participants judged future bad deeds more negatively, and future good deeds more positively, than equivalent behavior in the equidistant past. In addition, participants thought that future unfair actions deserved more punishment than past unfair actions, and were more willing to sacrifice their own financial gain to be treated fairly in the future compared with in the past. These patterns were explained in part by the stronger emotions that were evoked by thoughts of future events than by thoughts of past events. (more)

This is a form of hypocrisy, in that we pretend to be more offended by the fairness or morality of actions than we will actually be after they occur and can reward or punish them.