> surely I can’t impede law enforcement because they haven’t justified their authority to me

Unless you've broken the law (and certain special cases), they have no authority over you. Because of the nature of their jobs, which requires them to sometimes take away a person's freedom or life, they must be held to a much higher level of accountability than your average person.

You cite fear of harassment as a reason for not standing up to police, and to me that says something is deeply wrong with our current system.