Your lovely friend, who doesn't present as a woman, asked and was made happy by using the women's loos.
Ok. That's nice for him, and I can see why that seems a kind thing to do to make him happy.
Now imagine that it wasn't a single cubicle loo he asked to use, and there were women in there who were deeply uncomfortable to pee, have a poo, change a tampon, wash blood stained hands, have a miscarriage, with a man presenting as a man in the room. It isn't just about your lovely friend and his feelings, those women have feelings too. It isn't the job of women to put themselves second to make a man feel happy.
There are undeniably a number of sex offending men who have raped women and committed serious sexual offenses and are choosing to identify as women suddenly in adulthood with no history of gender dysphoria, often with obvious gains which they have openly stated, such as access to victims. The prison service shares this information, it's in the public domain to read. So no, not every trans identified male is someone safe and to be trusted in the way that women are used to trusting transsexual people who have been using women's toilets for decades.
Not all trans identified men are lovely. Take a look at Terfisaslur.com and think about whether you want to be shut in a room with one of the 'die in a fire cis scum' ones. Some of what the TRA people say is truly shocking in its violence and anger against women.
If society accepts that any man who looks and acts exactly as a man but says he's a woman can stroll into any bathroom and changing place, then it's inevitable that sex offenders who are not trans at all, will gladly take this open door into women's spaces. In the months since Target, the American store, made their changing rooms self ID the number of voyeuristic and sex based crimes against women has doubled to tripled.
Sex based protections for women cannot be casually undone without massive negative consequences for women, and as you can see on this thread, for Trans people themselves.