In response to replies about Marks & Spencers setting up unisex changing rooms.
"Sex is binary. There are only men and women. You can't change someone's sex."
That's not what trans people are asking for
Nobody is saying you can change your sex. I mean, technically we are all female when we are conceived, and then the XY chromosome triggers testosterone, but apart from that, sex is probably immutable... in humans. It's not binary either, because you have intersex people and many other factors.
However, changing sex isn't what trans people are asking for.
Trans people experience gender dysphoria
What they are asking for is to help them feel comfortable in the gender that the gender dysphoria they experience tells them they are.
Studies show that trans people typically appear to have a brain that matches the pattern of the gender they identify as. So it's not just in their mind, there is a physical difference between the brains of men and women, and trans people seem to have the opposite brain.
Nearly half of all trans people have attempted suicide, and this is because of the discrimination they receive. The hatred they endure on a daily basis makes them physically ill too.
And some just can't handle it, which is a huge shame, that people aren't being accepted by a society just because it's how they were born - some even submit to performing surgery on themselves because of how disassociated they feel in their bodies and the sex people say they are.
Being trans is not a choice
But even if there was no evidence we found to physically prove someone was trans or has gender dysphoria, why should we not believe someone? We don't currently know what makes someone gay, lesbian, or bi. And we respect other people who didn't choose how they were born either, like if you have a disability, or their race. Then there are some things we protect that we don't have control over like age, religion or belief. Same goes for what someone says their favourite colour or flavour ice cream is. Then there's stuff that is protected out of respect, like marriage or civil partnership, and pregnancy and maternity.
So because trans people don't choose to be trans, they've been observed for thousands of years, in other species too, and they tend to have a poorer quality of life, and basically out of sheer respect that we have for each other (and it's really not a lot to ask to basically trust someone when they share how they identify), it seems completely fair to prioritise gender over sex in basically all social situations. Do we need to know what's in their underwear?
"Too many men violate women"
The slippery slope fallacy
So I'd like to point out a likely slippery slope fallacy in your argument - that there are "too many" men violating women. I agree with you, there are way too many attacks on women - however, firstly, the majority of attacks on women are not in safe spaces. The top places to be attacked are in the home (domestic), parking lots, and generally outside e.g. parks, on the street. All of these places are gender neutral. The number of attacks in changing rooms is very rare. And the number of attacks by trans women on cis women is even rarer.
The overwhelming vast majority of trans women don't attack cis women. If anything, trans people are actually more scared of cis people than you are of them, because they terrified of being judged and rejected by society.
But if we take your logic, shouldn't we ALL men from from spaces women use? No, because it would be a slippery slope to assume that every man will attack a woman - because attacks on women overall is about 25%, which is the minority. So overall, most men are trustworthy, and it would be disproportionate to ban men from basically all public spaces. We don't have statistics for how many trans people there are, as so many of them feel do not feel comfortable to out themselves, because of how unaccepting we make them feel, but statistically the fraudulent ones are an an extreme minority of them.
I'm not saying that fraudulent trans women don't exist. However, to judge all your views on trans people based on a really small subset of them, and then pair them with the bigger problem, cis men, is not a fair conclusion to make. In the same way we don't assume that every Muslim person is a terrorist, or that every person wearing a hat is a pedophile. To do so is to stereotype, jump to false conclusions, and underrepresents the vast majority of law-abiding, good-willed citizens who aren't like that
So therefore, for the overall number of trans people exist that are law-abiding and good-willed, we shouldn't let the fraction of them ruin it for the others.
Conclusion
Trans people just want to feel accepted for who they are, more than anything, and I'd argue that it's ethically and morally wrong to not trust what trans people say. In nearly all cases, having trans women in women's spaces, which is one of the far few places that women are attacked, should not be a major concern, and is actually a distraction from the far larger problem of domestic abuse.
