Well, if you’re worried about long lines, I can assure you that M will be quicker in the can than natural ladies, since M won’t have menses or pregnancy complications to deal with, and every transman who uses the men’s room will bring those problems there instead.
And since we’re assuming M is a transwoman, I’m not suggesting allowing any males into a female space. I am however, very interested in protecting women from men who would sneak into a bathroom for the purpose of assaulting them. I don’t believe that has anything to do with respecting transwomen.