If someone is happiest presenting themselves as a blegg then that's how they they should present themselves and that is how others should treat them. The question of whether they are "really" a blegg or a rube is completely orthogonal.

In any circumstances? If I'm happiest presenting myself as a paperclip maximizer and I'm not should I do so? If I'm happiest presenting myself as a biochemist and I'm not is that ok? I agree with the sentiment in question as long as we are discussing sexual and gender identiy, but it seems to me that you are making too general a claim.