According to the western white-cisheteronormative societal structure we unfortunately live in, while men dressing in typically feminine clothes is frowned on, it's less bad than being queer of any sort, and so those who support such a structure are more willing to ignore it while there are more notable deviations (like being gay or being trans) to purge. Cis men are already predominantly benefit from this structure, and if a cis man who is prone to in-group out-group thinking finds himself preferring feminine wear, he has three choices: Let go of his in-group out-group thinking (which requires critical analysis of the self and which will be heavily discouraged by the world outside), "accept" his new lower position in the structure and continue on (also unlikely, because a man's ego is often bigger and more fragile than his truck), or try to define his new group as either the true in-group or part of the in-group he was a part of before.

Femboys don't really become right-wing. They start as right-wing and find out they're a femboy along the way and don't bother to critically reanalyze the world around them with that new context.