As I understand it the keystone between left and right is that:
The left belief is that all people are created equal and should have equal authority to point out wrong doing. The right belief is that people should be in a hierarchy with people at the top exerting control downward.
I think they are actually just saying if you really believe everyone is equal you can’t pick a group to target for mass murder. But if you are at the top of a pyramid tge people below you naturally look expendable.