Mick Hartley

The British Psychological Society – Cisnormativity impacts core emotional needs of transgender and gender diverse people:

Despite thousands of years of diverse gender expression, many trans and non-binary people still grapple with the impact of cisnormativity: the belief that cisgender people (people whose gender matches the body they were born with) are 'normal' or 'right', while others are not. The pressure to conform to this expectation can significantly affect mental health: societal messaging around gender being determined by biology, for example, may affect someone's ability to feel safe and happy as themselves. At a time when trans people are also being asked to "accept perceived reduced rights", this is more important than ever.

Oh god. It's that "gender being determined by biology" which is doing the damage here. Sex is determined by biology. As for gender, well, in its usual meaning nowadays as, basically, sexual presentation in the cultural climate you're in – dress how you want, present yourself how you want. Live how you want. But you can't change your sex. 

It's not that hard. Really. Unless you're a psychologist.

Added: to spell it out….this sex/gender confusion has devastating consequences.

The old way: if you're a girl who likes cars and playing football, and doesn't like dolls and girly things, then…*shrug*. So what? If you grow out of it after puberty, fine. If you don't grow out of it after puberty, fine. Maybe you're lesbian, maybe you're not. Whatever. You'll find your own path.

The new way: if you're a girl who likes cars and playing football, and doesn't like dolls and girly things, then…this means that you're a boy. That's because real girls don't like cars and playing football, and do like dolls and girly things. So you need to transition. First the puberty blockers, then the hormone replacement, and then, very likely, the surgical mutilation. You'll be sterile, your sex life will be problematic at best, and you'll require constant medical attention for the rest of your (shortened) life. 

It's not hard to see which side here is governed by "societal expectations" and gender stereotypes.