This is really common, unfortunately. People who are raised being abused, or being excluded, are taught that those in power should abuse or exclude those not in power.
Naipaul wrote about this when he was talking about post-colonial societies that ended up as brutal as the white man they replaced. "Hate oppression but fear the oppressed."
Just because some people are oppressed, it doesn't mean they are all nice and pleasant otherwise. "Noble savage" is a western invention, but many undeveloped (from out POV) societies are brutal, violent and harsh without any external influence, just by themselves. Being brutal is natural, being nice comes later.
