I want the peaceful and kind and gentle trans people I know to be able to live their ordinary lives in their chosen gender in a way that doesn’t hurt others, without being harassed or rejected, or humiliated by being forced to use the toilets of their birth gender.
I'm going to unpick this a bit.
Firstly, it's not about the bloody toilets. They have just become a stupid symbol probably because they are one of the first single sex rules children encounter so "winning" the toilets has psychological and cultural significance. It's about the right of female people to say at times we need physical or cultural spaces away from male because male people encrouch on us and speak over us in ways that harm us physically and diminish our social power and agency.
Ok, with that out of the way:
Why the assumption that using the toilets of one's birth sex is "humiliating"? That just - isn't a thing, or at least it wasn't. The only reason it became humilating to trans people is because it broke the lie/fantasy that they were the opposite sex. It's not the use of the toilet that is the cause of the humiliation, it's the being exposed in the act of their fantasy/lie. The fix is super simple - don't lie about your sex, and the humiliation of being known to be your sex goes away.
Living in a "chosen gender" is just adopting your own sexist projections about the opposite sex. It's not a real thing, it is an insulting and reductive performance. We should be broadening what is socially acceptable for each sex in terms of traditionally gendered social roles not pandering to the idea that liking things coded to the opposite sex means you mentally are the oppsite sex!
My DH happens to be a peaceful and kind and gentle man with a build that would blow away in a strong breeze, the type of bloke that some men like to pick on because it helps them feel powerful. He is no threat to anyone, male or female. Given the option I'm sure he also would prefer to use the ladies because it's a little less intimidating and an awful lot cleaner. What is the objective difference between a peaceful and kind and gentle man and a peaceful and kind and gentle trans women that justifies the latter coming in but not the former?