The idea that you already know everything there is to know about oppression or that you at least know all the kinds of oppression is harmful not just because it prevents you from growing as a person but also because it feeds into REG rhetoric and behaviors. I’m going to use REGs of the aphobic variety as my examples because that is what I am familiar with and can comment on, but I suspect it applies elsewhere as well.
How many times have we heard someone claim that the acronym is just LGBT, as if that proves that no other group can be oppressed for deviating from cisheteronormativity?
How many times have we seen REGs stubbornly dismiss stories of aphobia based oppression including corrective rape because if a spec people really were oppressed they would have heard about it before hand. (I really do get the sense that REGs believe that if you were really oppressed, you wouldn’t have to prove it, which is exactly what this mentality entails).
How many times have we seen people mock the struggle of erased groups for recognition as if by being erased there is no way they could experience any form of ‘real oppression’. As if that doesn’t directly feed into the erasure that the groups are facing. Because this of course harms erased groups immensely, though because oppression often works by saying ‘they aren’t really oppressed cause they deserve it/we’re right this time’ this isn’t exclusive.
But, the sad thing is those statements make a whole lot more sense if you buy into the idea that the only types of oppression that exist are those that you’ve already deemed worthy and no others. The idea makes discussion of new forms of oppression not simply a new discussion but a refutation of the claim ‘and no others’. Because people hate being wrong (often despite thinking they don’t), and because society encourages aggression towards marginalized groups (especially if not questioned), these beliefs can lead to hostility, ready to be fanned by the REGs.