Although I understand how it feels like an insult, it's a way to bring changing a gender to the masses. There's a long way to go to fix this problem in society, where a lot of people are still unrightly fearfull of transgender people. One of the things TOS did was bring outlandish ideas (back in the day) as common in the 23rd century. To our standard right now, a lot of what TOS did was sometimes quite insulting. It did however, inspire a lot of people to think differently. Mostly the young minds.
If showing a alien character that changes gender as something that's quite normal, young minds right now will think of it as nothing but normal.
It's going to be incredibly hard to change the rights for transgender people in the course of a year or two. However, if small examples like humans reacting very casually to genderchanging aliens will somehow affect the minds of young adults right now, the same young adults who will shape our future, I think it might just be something inspiring instead of insulting. I also understand that's very easy for me to say, as a straight male, really. Don't think that I'm not taking your experiences into account. I'm aware of some of the things you've posted on the forum, and I'm not trying to attack you. Just trying to look at it from a different angle.