I'm not really "transphobic" per se, I just see it as promoting narcissistic behavior and taking all kinds of people down the wrong path in mental help. It's not the "gender dysphoria" inbuilt condition that I am in disagreement with, that can definitely happen because sex chromosones can not develop properly and screw with the brain and hormones, or there's exceptional cases related to trauma, yadda yadda yadda, it's the idea that that person somehow is the other sex because of having that condition in their mind is where I stop agreeing. It should be like how it was treated before the DSM-V, as a mental disorder to manage and not some kind of social identity that someone should build around. To me it's like telling a schizophrenic that instead of saying "the voices in your head aren't true, we'll help you in trying to manage them" instead they decide to just say "yeah, the voices are perfectly fine and natural, we'll make sure that the rest of society agrees with that worldview", which is against all logic and helps nobody.
And of course, there's the segment of people that I believe don't actually have the gender dysphoria condition which makes up the vast majority of troons and pooners nowadays. Especially online, anywhere you see them it's just the most self-centered groups and behavior that I've ever seen. Those people tend to crowd in their own communities to echo chamber off each other, and they pull people that have similar interests to them, usually the ones that already have autism or are otherwise isolated socially somehow, and infect their minds, taking away anything diverse they once had and making them the same loud nightmarish shitheels as they already are. This group is the group that I honestly wish would just all go drown in the bottom of a lake somewhere. They all get to hide behind the troon identity as well, any criticism of what they do or how they go about their lives gets you an instant "transphobic!" label and you're now a persona non grata.
I will never, ever accept a transgender identity as a legitmate thing even if it was just the ones with an actual severe mental condition, but it's that second group that turns me from "I dislike the system that's being pushed upon everyone, but I sympathize with the people suffering" into "I wish they would all die off and stop infecting society and everything that I enjoy".