A logical fallacy stating that, since a person belongs to a group who is currently oppressed, or has a long past history of being oppressed, than he cannot be an oppressor himself or, vice-versa, that since a person belongs to a group that is known for oppressing other people and/or having oppressed other people in the past, than he cannot be a victim of oppression himself.
What this fallacy does is prejudicially discriminating people into "eternal victims" who can never do wrong, and "eternal oppressors" who can only do wrong, and is therefore both a stricly right-wing position and a form of oppression itself.