“Sex segregation doesn’t help – if a predator wants to assault someone, a sign on the door won’t stop them.”
This objection fundamentally misunderstands the purpose behind sex segregation as a concept. No one believes that marking a space as woman-only forms some sort of magical barrier against male violence. Instead, woman-only spaces allow for potential threats to be identified and dealt with before a crime occurs, rather than afterwards. In a mixed-sex setting, any man can enter an intimate space with women present, and those women will be unable to object; until he actually harasses, assaults, or otherwise abuses them, they have no recourse. In contrast, sex segregation allows for men (who are responsible for the vast majority of violent crimes, especially in intimate spaces) to be removed immediately, before they commit a crime. This alone makes sex segregation a valuable tool in the fight against male violence, and statistics back up its efficacy.
As a comparison, consider the concept of a gun-free zone. Does anyone think that forbidding weapons in malls, schools, or places of worship will discourage a spree killer? Of course not! No one who is set on committing mass murder is worried about a misdemeanor weapons charge. Nonetheless, gun-free zones are still important because they give legal grounds for police or security to remove potentially dangerous people before they open fire. The same is true for sex segregation – it exists to provide women with legal grounds for removing potential threats, not to appeal to a predator’s conscience or fear of breaking the law.
It’s also worth noting that, while the debate around sex segregation often centers around the idea of calculating predators intentionally following women into intimate spaces to abuse them, most sex crimes are actually opportunistic – situations where the perpetrator finds himself alone with a woman and makes a split-second decision to commit an act of violence. So while a sign on the door might not stop a predator from intentionally seeking out victims, it absolutely can prevent opportunistic offenders from encountering vulnerable women they then decide to harm. Sex segregation is perhaps most effective in these situations, which makes objections like the one above even more irrelevant and dishonest.