- envy, these guys would like to get into the ladies themselves.
- Carrie Paechter's concept of the masculine gender being policed more strictly (both going in and going out) than the feminine one.
- The old-fashioned sexist idea that these guys have to be protective of "their" women against people they perceive as men.
However I believe the reason is much more simple than that and is related to power. If you take a walk through St Ann's Square in Manchester there is an interesting historical relic which gives us a clue. A very old, early Victorian, public toilet. It is now disused and they have put an electric substation down there or something like that. But notice how I said 'toilet' in the singular. There was only one of them. For men. You can see this repeated if you go into some very old pubs like The Ship in Wardour Street London; there was originally only space for one toilet and they have had to make space for two giving the back of the pub a rather cramped feel.
During much of the Victorian period public toilets existed only for men and there was a reason for this; to control women. Public toilets allow people to stay out, away from their home, for long periods. This meant that men were able to travel, to work, to do business, to engage in political and civil activity in ways which women were not. Women were effectively only able to do the shopping and go home again, they could not spend long periods away from the home. Indeed not having women's public conveniences became so 'normal' that women attending Ladies Day at Royal Ascot would not wear any underwear because they would need to 'go' in a corner of a field behind a hedge.
This represents the situation today for transgender people; not being able to use a public toilet represents a restriction on one's civil liberties. The fact that men are the ones most concerned about this issue strongly suggests that it is a power issue rather than an issue of public safety for women; men, most of whom are termed 'gender defenders' by Kate Bornstein, would like to see transgender people's restrictions on taking part in civil and public life restricted by subtle means since they cannot argue for restrictions on transgender people's civil rights in other ways.
Toilets may seem a relatively trivial issue, but it is an important issue of civil liberty and human rights; the right to take part in civil and economic life depends on being able to spend long periods of time away from home during the day which in turn depends on easy access to public conveniences in the same way that cisgender people have.
Despite transgender people's run-ins with some feminists in the past, I believe trans people have a lot to learn from feminism, in particular that pretty much anything gendered has a power element to it as well and that male hegemony wants to force its way into the most unlikely places, including, in this case, the ladies.