If they are just clothes, then it's fine for someone who identifies as neither male or female to use either changing rooms.
Otherwise it's just saying that the clothes define my identity.
In which case any woman trying on a pair of trousers should use the men's. Or is the defining factor what labelling someone decided in a factory. In which case gender is decided by third world fashion factories and fashion buyers? Is that what we are saying?
Or are we saying that women who feel uncomfortable with bearded penis havers with gender stereotyped ideas of what is male and female don't matter and should have to put up with males in the women's? Cos that sounds remarkably like sexism ...