It's very simple. If you want to do (professional) sports, you cannot take steroids/testosterone.

Being trans isn't a choice, but taking testosterone or whatever definitely is. It does not matter if you're male, female, trans, chinese, african or american.. Nobody should be allowed take banned PED's in professional sports.

It is very important to keep this integrity in sports. You could argue that you can let a FtM take testosterone because else he wont be able to compete with the others, but what if he started winning. Will people say he won because he's so good or would it be because he's allowed to take testosterone?

No ifs, no buts.