Glorianny
Oh dear now non-binary people are a threat to society!
Who knew??? I must take care not to meet any more of them.
Maybe they will take over the world!!!
Maybe they will stop children identifying and classifying people by gender norms.
Maybe you won't be able to tell who is a boy by what they are wearing!
Maybe boys will wear make up and jewellery but we won't know they are boys.
Maybe girls will wear trousers and shirts and look like boys. Maybe the gender norms which restrict our society will be overwhelmed by non-binary people.
But hang on!!! isn't that what some people want? A society where people are treated equally? A society where gender isn't an issue. Ah well back to the drawing board 
You remember how we used to have a polite agreement about toilets & changing rooms, so that people used the correct ones for their sex?
And a polite agreement for things like women-only self-defence classes or women-only creative writing groups or women-only swimming sessions, so that men didn't turn up to those things?
Why can't we still have that, regardless of how people look?
It would involve some trust, of course, if we genuinely can't tell which sex someone is by looking at them but it wouldn't involve obviously male people insisting on being accepted as if they are women.
How about single-sex hospital wards and single-sex prisons? It's very unlikely that those in charge of such places don't know the sex of people they are dealing with, however they present themselves.
A few pages back, on this thread, Glorianny, you said 'No-one is talking about changing sex' but that's exactly what is being claimed - that people are the sex they choose and society should be organised around their choices.
Instead, imo, people should present however they like, as you say, and should be honest about which sex they are when it's important.
