Why do women seethe so much when realize the man they like is interested in men as well? They lose all sexual/romantic interest in them and see them as fags. Even if they are bi they think them as just "gay".

Does bisexuality in men really exist?

All the bi guys I met (7) either liked women and trannies/femboys or women and manly men. The second group was primarily gay and preferred full grown men with beards, muscles and only dated men once they started hooking up with men too. While the first group was basically straight and occasionally fapped to shemale porn (two of them also banged some trannyhookers but they came back to females after a while because tranny butt couldn't compete with pussy).

It seems like "bi" guys are either ashamed gays or porn-addicted/desperate straight men.

Bisexual men are a meme. They're either gays in denial or straight men who will go to desperate lenghts to get their dick wet. Either way it's a perfect recipe for getting an STD, cheated on, or having the kind of relationship drama an effeminate man brings into the relationship. M/M/F threesomes actually sound pretty hot but it's obviously a bad recipe to be in a relationship, it's more a casual degeneracy thing.