The tendency of bystanders to avoid intervening in conflict, even though they would want others to intervene on their behalf, can be best explained by:

cognitive dissonance theory.

Explanation:

Cognitive dissonance theory explains why people face challenges to accept new information which is contradictory to the belief they hold or act in a way that undermines their self-image. Therefore people tend to feel dissonance when their consistent perception is challenged by hold truth or action and they try to reduce this dissonance. For example, a religious person feel uncomfortable when an atheist disrespect sacred images.

As per the question, the instances of bystanders not intervening (an action), even though they would want others to intervene for them (a value) is a classic example of cognitive dissonance theory.