In fact, the way that we go into public toilets in this country is simply a matter of convention, and if we are uncomfortable with someone who is using a space that we don't think they should be in, then perhaps we can ask them about it. But even then, we must be careful. There are many stories from butch lesbians, or butch heterosexuals, even, who have been challenged in toilets when they are in the toilet that is entirely appropriate for their gender, so we must be careful about that convention as well.