Actually, it is for us to decide what we are going to call someone. No one has bothered to even explain how:
1. A man or a woman knows how the opposite gender actually feels, how they think. They can't, they can only mimic what THEY believe the opposite gender feels and thinks.
2. A man or a woman literally becomes completely and totally the opposite gender when all they did was claim to be and altered their appearance.
3. If a person LITERALLY and COMPLETELY becomes the opposite gender, that their sexual preference does not switch between homo and heterosexual. Is that orientation mysteriously prevented from changing, thus rendering the claim that they actually became something they are not null and void? Think, someone claims to be a woman, totally and completely. They like other women. Are they a lesbian? Apparently not if they are a complete woman, but used to be a man, but didn't switch preferences, but can't be distinguished in any way from other women. Do you not see the contradiction in what you are claiming?
4. If a person LITERALLY and COMPLETELY becomes the opposite gender, why do they cling to the title "trans"? Should they not drop it and just claim to be the gender they want to be?