Bad energy and cultures of cruelty become solidified through identity and persist. For example, cruelty emerges within constant turmoil that cannot be readily solved by the individual, such as being in an institutional setting in which people are being harmed and nothing can be done about it.
Witnesses in such situations can transform in many different ways, some of them very positive, which is more rare. What tends to happen though is that the witness is put in an impossible position, and unable to do anything about it, shrugs, and remarks, "that's just the way it is."
Now that individual is bound by ego to be cruel, because that is what one must do to get by, and such an attitude outlasts the actual point of cruelty and persists, producing more cruelty in turn.