How would you feel if you encountered a transsexual in a changing room?

Suppose you were in the changing rooms at a gym, fitness centre or even the changing rooms for trying on clothes in a store. And someone comes in who is clearly pre-op transsexual and trying hard but doesn’t pass as their chosen gender. (To clarify, if you’re in the women’s changing room this is a male-to-female transsexual. If you’re in the men’s, it’s a female-to-male).
How would this make you feel? Would you feel that this person belonged in the other changing room instead?