So much good sense being expressed on this thread!
For me, it's the lies. Not just the fundamental one, that humans can change sex. Lies start off by corroding trust between people and spread to corrupt institutions.
Obviously anything founded on a lie has to be supported by more lies, eg calling men 'she', falsifying official documents such as passports and birth certificates, allowing men to claim prizes in women's sports etc etc.
And these then have to be supported by people pretending to believe them, like the NHS staff who swore, when a patient said another patient had raped her, that she was lying because there were no men on her ward (the rapist was a 'transwoman').
And if you play along pretending to believe the lies, you have to denounce those who won't play the game, and they have to be punished. So even if you want to stop lying, it gets harder and harder to dare.
To shore up the lie -
Organisations have to exclude members who commit 'wrongthink'
Employers have to sack guiltless workers.
Colleagues have to shun colleagues.
Trade unions have to abandon their female members.
Police have to interrogate those who express conflicting opinions.
As the lies spread to disrupt society -
Women's single-sex organisations and spaces have to allow men in.
Lesbians have to accept male sex partners or risk being excluded.
Laws against indecent exposure have to be quietly ignored so men can freely parade naked in front of women and children.
Children are taught that people can be 'born in the wrong body' and need drugs and surgery to put them right.
Governments pass laws to entrench the lie, eg self-ID
Etc
At every level, as the edifice grows, I suspect the pretenders feel more and more desperate, but no longer dare to challenge the lie.
It will all come tumbling down eventually, because nothing built on a lie is stable. But many young lives will have been ruined before then.