But as nobody has said that in general, people shouldn't be able to have surgery if they choose, then the only thing you could have been arguing is that you think children should be able to as well, as the other clearly happens already.
I don't personally think surgery is the right thing for people with dysmorphia, but it's legal and people do want to do it. What I object to is the idea that it actually makes them the opposite sex, and that they should have access to women's spaces as a result.
I'm all in favour of them looking how they please, being called by whatever name they please, and doing whatever jobs and hobbies they please. Just that it doesn't actually 'transition' them into the other sex.
But I don't think people are arguing against the existance of trans people, or the fact that they are allowed to change their bodies as adults. I may not think it's the right thing for them to do, and I might worry about the effect it has in society of entrenching gender roles, and the consequent effect on children, but that is not the same as arguing that adults can't dress/present how they please, if that makes them more comfortable and doesn't intrude on single-sex spaces.