From my experiences, I would say that girls are, on average, more open than guys are. I think it has mostly to do with socialization.
Usually, when a girl harbors transmisogynstic feelings, it's because we make them feel insecure with their femininity. They think, "How dare that MAN even try to be as pretty/feminine as me?" It kind of shakes the very foundation on which they stand, so to speak. I find this to not be very common, and when girls harbor these types of feelings against trans womyn, I notice they are usually harboring lots of internalized misogyny.
It's a lot more complicated with guys. We make them feel insecure with their masculinity in a very big way. The reason why MTFs are so demonized by our culture at large is not only because their forsake their own masculinity, but also because they forsake the masculinity of straight men. The patriarchal society holds male heterosexuality to a sacred status. Men who are socialized into toxic masculinity are socialized to see womyn as a commodity that defines their machismo. The more the womyn meets patriachal beauty standards (thin, white, cisgender, conventionally feminine, etc.), the more "value" she has in terms of defining the man's machismo. If a womyn somehow fails to meet those beauty standards, she takes away some of his machismo. This is why overweight, non-white, butch, etc. womyn are so demonized. To put it from your stereotypical toxic masculine frat boy perspective: "Look at him, all the chicks he's scoring are ugly fat chicks. Something's wrong with him, he must be gay." When trans womyn are involved, it's a lot more extreme, because it's not that he MIGHT be gay, but rather, that he IS gay. From the toxic masculine perspective, being gay is the ultimate failure of machismo: gay men are unable to to objectify womyn into a commodity or object status, and are thus unable to live up to one of the central expectations of the toxic masculine gender role. This is why trans womyn inspire such intense fear and hatred among men who are heavily socialized into toxic masculinity. From their perspective, trans womyn "trick" them into being gay, and take away their valued toxic masculine status. The reason why hate crimes happen is because once that happens, the only way they can gain back that toxic masculine status is through violence.
Now, even though all men are exposed to toxic masculine socialization, there is a huge variation in how much they embrace it. There are plenty of men who see past all that BS and therefore are totally accepting of trans womyn. However, if you compare the extent to which men are expected to conform to toxic masculinity versus the extent to which womyn are expected to conform to toxic femininity, men are FAR more pressured to conform toxic masculinity. These differences in socialization are why I believe that girls are, on average, more accepting than guys.
