"Couldn’t the same argument be made about trans people use the they want? You might be uncomfortable when you see a trans women in your toilet, but you can’t expect to never feel uncomfortable."
Well no, of course the same argument can't be made (unless you want to look like a complete fool), because it's the law that males stay out of female single sex spaces, and that is because of the fact (not a feeling - based on data and other evidence) that females are at risk of harm when males are allowed in these spaces.
Trans women are not expected to stay out of female single sex spaces because they are trans. They are expected to stay out because they are male. Trans men, who are biologically female, are welcome. It's not a trans-exclusive space, it's a male-exclusive space and that is mandated in law, for very good reason.
"Let’s not forget that legal situation was different when most people transitioned"
It wasn't, actually. The law hasn't changed, the Supreme Court just clarified the meaning of the existing laws. It was lies told by the likes of Stonewall that led some trans people to believe they could go into the spaces that aren't for them. It has left some of them in a situation they're not happy with, of course, but that doesn't mean we should break the law.