There is a brand of cis women who are faux trans allies, with a lot of unconscious transphobia they don't address, who performatively/shallowly support trans women then quite openly resent trans men. Coming from a place of viewing us as "joining the enemy" and abandoning womanhood, and use their position as women "punching up" at men as an avenue/excuse to publicly express transphobia.
Time and again you encounter this cis woman who will only very performatively support trans women- fem presenting, passing, het trans women, that is. Or feminine trans sapphics who don't express any interest in them personally. Or sometimes for some queer cis women, they can be very chaser-y, and think fetishizing trans women, with an expectation of them to be non-op dommy mommies for them, is just a part of their allyship.
They often will not address nonbinary people, perhaps other than a performative "youre valid 🥰" (and can have a lot of exorsexist beliefs anyway).
And lastly, when trans men are brought up, they act with a lot of disrespect, entitlement, and disgust that I think a lot of people pass over waaaay too quickly.
They can very openly and condescendingly talk down to trans men, expressing covert misgendering ("when he has he/him pronouns but I can't stop looking at his huge tits 😂") and plenty of overt malgendering as the justification and thin veil over their transphobic feelings towards trans men ("stop mansplaining, I guess trans men really are men" to shut down when a trans man joins in on a conversation even in a totally benign way- they don't respect him and want him to participate.)
It's a lot of "yeah sure you're valid as a man, so I'll treat you as a man (very cruelly) hehe 🥰" projecting their resentment and anger at cis men/patriarchy towards us, but alongside a lot of societal transphobia repackaged. They also still tend to speak of trans men with more vitriol and demeaning language than they do to cis men. Because we're easier targets, because there is a lot of disgust in society for us they have taken on unconsciously, and they excuse it.
They seem very uncomfortable with addressing the fact they have power/privilege over us, some even assume/project the opposite, and operate off of a perspective based on the idea we transition and gain privilege, expressing it consciously or through implication, sometimes that we even have transitioned in order to gain privilege- that it's at least a motivating factor.
So again, there's this resentment, this internalization of the idea we've betrayed womanhood, and this disgust at masculinity and masculine gender nonconformity. Because of the gender essentialist connotations with masculinity universally being privileged, violent, and a representation of the hegemony. Gender nonconformity, trans manhood, is especially egregious- you had womanhood (and attached femininity with that) and you chose otherwise.
Trans women are a rebellion against gender conformity they can understand better, because they understand femininity is in contrast to an establishment ruled by hegemonic masculinity. They see trans women as "giving that (privilege/manhood) up." Which is still a flawed perspective with a very "before you were a man but now you've sacrifice to 'chose' to 'become' a woman" vibe. A very "now you know how we feel" vibe. Self centered.
But transmasculinity, especially trans manhood, can only ever be a joining of the hegemony, ""joining the patriarchy."" They do not recognize or accept masculine nonconformity as radical or subversive because to them the whole of masculinity represents toxicity, cis men, and cisheteropatriarchy.
Because their feminism is, frankly, self centered. Their perspective of gender revolves around a deeply cis-centric view, an often very feminine view too (without genuine regard for even cis butch women, much less trans butches). They think first of themselves, and interpret others experiences off of a position most familiar to themself.
They have idealized femininity and womanhood to have a purity that, ironically but integrally, teeters from solidarity into intense carry overs of regurgitated gender roles. Men as masculine, dominating, unfeeling, aggressors and women as feminine, passive, kind/emotional, and only ever victimized.
Which is why they feel so remorseless about expressing transphobia about trans men as long as they're "affirming" their manhood, because to them, as women, they're only ever victimized in regards to gender, and cannot be the ones victimizing another in a gendered dynamic. Especially a man.
Although, again, with their shallow allyship to trans women, when they do encounter a trans woman they don't like, they're quick to view that trans woman as an aggressor and their attacks against them as just self defense from a position of victimization. Justifying their transmisogyny as long as they "yass queen" the "good ones." Or that someone alleges the trans woman in question isn't truly a trans woman, so they're really only attacking a faker, a man with privilege over them, and some internalized motivating evil.
They seem to frequently dangle a sort of conditional acceptance for trans men only through the circumstance of their usefulness to women. Like our existence's job is to teach cis men not to be misogynistic or protect and uplift cis women (with the distinct impression that we ourselves are not in need of a mutual protection, that we have some voice or armor or power they do not). "Before you were a woman, but now that you 'chose' to 'become' a man, you owe us" position.
We're also held at a sort of rhetorical gunpoint, that we have to constantly prove ourselves as allies to them and never speak up too loudly, never try to stand on equal footing to cis women, because we need to be obedient to women, act as a "good man." Unobtrusive, unheard, decentered, lest we get accused of doing as misogynistic cis men do.
We're insisted to fight the influence of misogyny within ourselves, but that insistence is because it's believed that maleness will just instantly start funneling misogyny into us (because misogyny is stored in the manhood). We're a danger in wait unless proven otherwise, especially since we "chose" this, and this is another reason they can be cruel. Again, this sentiment is far more often and more strongly expressed about and to trans men, than cis men.
Their refusal to address their own privilege over trans men and cis-centric perspective of men always are on the top of the hierarchy makes it so they easily fall into the belief of trans men having a lot of ease and privilege over trans women. Then there are instances where a trans woman expresses this sentiment (someone who views the oppression of trans people competitively and prioritizes her experience, and doesn't understand/respect trans men's oppression).
Especially if this trans woman expresses resentment of their own to trans men, then these cis 'allies' see it as the go ahead to unleash a lot of transphobia towards trans men they feel, but now in a seemingly acceptable situation. It's just the same as when cis women do it to cis men, right? Punching up? They have permission from a trans person now though, an alleviation from that pesky trans-cis dynamic they technically have with trans men. The doors get opened.
Sometimes they'll frame it as if they're a third party just snarking in supposed allyship or 'defense' of trans women, by still being deeply transphobic to trans men, but they'll also sneak their way in to speak with such an authority that you wouldn't realize they're just cis without looking into their profiles.
When it is shit on trans men hour, these cis women come out of the woodworks and they're eager to express a lot of the transphobic stereotypes about trans men they've held onto. Their allyship to trans men begins and ends at feeling we are allowable targets for their resentment because of our manhood.
They really haven't made any real effort to unlearn gender essentialism, just sort of boiled it down to woman good man bad. They get to feel this way and say these things, not only because they're "man bad" and they're an ally so they're just "affirming" us, but also because we've earned this, deserve it, and invited this by the very act of choosing manhood when we should metaphorically "know better."
But this treatment reveals a huge issue with their general perspective of gender, and gendered oppression -- and ultimately an "ally" like this will always end up unsafe to all trans people.