Those who are sexual predators and not undergoing hormone therapy and are "trans" with an ulterior motive? Like I said, they will find a way to get to their victim regardless of single sex spaces.
I keep hearing this argument and that if assault does take place in single sex spaces then women should just report it and have it dealt with that way.
But thinking about the sexual assault and harassment that is carried out by strangers in public places we know that these things are opportunistic and tend to happen in places where women are isolated or vulnerable. Public transport, parks, isolated areas etc. The experience is often fleeting and hard to evidence. The sorts of things I mean are getting groped/touched, being flashed, being masturbated at, being watched. We also know that the vast majority of this less severe sexual assault / harassment against women goes unreported.
The trouble with opening up single sex spaces to anyone who identifies as a woman is that this will also include the sexual predators with "ulterior motives" that you have mentioned. So aren't you are just making it easier for these sexual predators to carry out their abuses and get away with it?
The very nature of single sex spaces (presumably with the exception of prisons) is often that there are no cctv cameras. Refuges, changing rooms, toilets, shared dormitory accommodation are all cctv blackspots and are the perfect place for sexual predators to "get to their victims". Any allegations made will be the word of one individual against another There will be no physical evidence unless a violent assault is carried out or unless there are witnesses. And as we all know it is almost impossible to prove sexual assault unless there is cctv/camera/phone/witness evidence to prove anything untoward has happened.
As a 50yo woman I have experienced low level sexual harassment by strangers in public places on numerous occasions and I have only bothered to report one of the more serious instances because I was worried that the person may have gone on to carry out a more serious crime. Nothing was done about it because the quality of the cctv was poor and it was not possible to ID the person or ascertain that they were doing what I said they were doing.
I cannot work out how concerns about opening up women's spaces to anyone can be deemed to be bigoted or transphobic. For me it is a 100% genuine concern based on my life experience as a woman.