Probably assholes who just hate femboys.

Ok yeah, I worded it a bit badly, I edited the text so it’s hopefully more clear.

No Invalidation Gender Identity. Specifically no calling people eggs, also known informally as egging, which is trying to insist that a femboy (or any other GNC person) must be trans due to being GNC

Basically it’s saying they must be a girl (trans) because they dress like one. Was a popular thing to do in r/Egg_irl a while back (at the expense of the femboys featured) which is where the term egg came from and why it became known as ‘egging’.