Being gay is a social experience centered around a culture of people who prefer their own sex. If anything you got it exactly backwards: it may be homosexual, but it's only gay if it's gay. As far as sexuality goes things like orientations are pure bunk - invented and very recent ideas that fall apart at the slightest suggestion of nuance.
Traps aren't very gay because, fuckn obviously, the aesthetics of m/m trap sex are pure hetero: one partner is masculine and the other is feminine, sometimes to the point of trying to imitate or even contextualize the sex as being a simulacrum of m/f sex. When you pedantically come along and say well hoo hoo it's gay cuz there are two men you're entirely missing the sexuality of what this niche is.
Bears and twinks are gay. Both of those aesthetics are straight out of gay culture, it's a purely masculine affair, and even if the twink is purely a bottom he's not trying to pass himself off as a woman or contextualize his relationship to his partner in terms of familiar straight dynamics. The sexuality of the act follows along its own lines.
It's not really that hard to understand. If someone's getting off to treating a soft boy like a girl and the boy is getting off to feeling (what he thinks to be) like a girl then they're experimenting with straight dynamics, not gay ones. No matter how much scared little straight boys want to push everything that seems gay away from them that's not how this works; gay people define their own niche and traps ain't part of it.
This would be a prime example of re-contextualizing somethings theory so much, that you completely lose touch with reality. Main reason being that your argument is so focussed on how wanting to have sex with a femboy doesn't adhere to your narrow view of "gay culture" that you're missing the part of it where a man is attracted to the idea of anally penetraring another man. Femboys or "traps" are generally not shown to actually consider themselves female, so we're not even getting close to the area of transgenderism. They are merely men or boys that happen to have feminine features and enhance them through the way they dress with, at least in most stories that involve them, the purpose of drawing the attention of other men. Likewise men that are into the idea of femboys are generally not of the opinion "Oh, I would have vastly prefered if this was a woman, but sure, I'll take the little bonus." or "Oh, so this isn't a transwoman but he actually considers himself a man? Fuck it, I'm too invested now, wanna fuck that character anyway." but the idea of the character being effeminate yet still clearly male is the whole appeal. I legitimately have no idea how anyone could consider that anything BUT a homosexual fantasy.
Your argument tries to avoid coming to that very same conclusion by proposing 2 "counter-arguments", both of which seem pretty narrowminded.
1. And this one, at least, is just implied in your argument and not straight up articulated: "Feminine men that have sexual encounters with other men are not homosexual, because you don't get to pick your sexuality if you have feminine features."
2. This one you essentially just stated outright: "Anything that does not adhere to my personal view of 'homosexual culture' (a.k.a. bears and twinks) is not acceptable as gay in my eyes."
Trying to defend either position without admitting to quite literally gatekeeping a sexuality, as another poster so wonderfully put it, will be pretty difficult.
You can technically even remove the "culture" aspect of it entirely, as that is one of those common cases of people mixing up sex and gender. Gender is the social concept, but that one is not being discussed here. There is no social checklist for being biologically male and there is no social checklist for being homosexual as both of these categories are solely commenting on the persons sex. Sex = born with the chromosomes and a set of internal and external genitalia meant for procreation that we have dubbed "male" or "female" respectively / Homosexual = prefering sexual intercourse with someone of the same biological sex. There is no culture involved here. This becomes a bit blurrier when taking into account transmen and transwomen, although by definition a man having sex with a transgender woman would also be engaging in homosexual sex. That does not change the fact that this transwoman would absolutely be female when talking about gender, it's just that the terms "sex", "heterosexual", "homosexual" and "bisexual" do, in their etymology, all focus exclusively on someones sex.
So if some men are fantacising about sex with other effemenate men, then they are very clearly going for a homosexual fantasy. They essentially created a scenario that might be 99% straight fantasy at first, but then specifically chose for the target of their attraction to have a penis, testicles, no vagina and to consider themselves male too. The only reason for those additions would be if you want it to be a homosexual fantasy instead.
Rather than trying to push this into a "this guy doesnt even play football, so he can't be straight" or "this guy acts like neither a bear not a twink, so he can't be gay" direction wouldn't it make more sense to simply accept that people of all sexualities can be pretty different in regards to their specific tastes?
You wouldn't tell a straight man that is into tomboyish women "woah, you don't like strippers and cheerleaders, so you're no longer part of the straight club now" and it makes just as little sense to tell gay men that are into effeminate men "that's neither a bear, nor a twink, so you're out of the gay club now".
