Because believing things and taking a position are different things, maybe? It's actually one of the hallmarks of a cult (like wokeness) that to become a member, you must openly declare belief in obviously false things. Religions are another good example.
The first is a factual statement (is versus ought);
The second semi-factual ("not justified" is a maybe subjective distinction);
The last is purely subjective, both in the "shouldn't" and the somewhat vague definition of "mental disorder".
That said, the furore around TS seems to be as much about enforcing terminology that appears to muddy-the-waters wrt biology i.e. what "woman" means, or should mean.
“Women getting paid less in the workplace is because they purposely pick lower paying jobs, not because they’re discriminated against”
“The BLM protests from last year were more riots than protests and were not justified considering the events that sparked them”
“Transsexual people are experiencing a mental disorder and this shouldn’t be encouraged or accepted”