Why do people care so much about how others wanna live?

First, they want to go after the kids. Kids don't have the ability to make life-altering, irreversible decisions based on what may just be peer pressure.
Second, a lot of gays are beginning to notice this seems to be a way of eradicating them. Scott Newgent -- @NotScottNewgent on Twitter -- had been a lesbian. He fell for the idiocy that he didn't really want to be a lesbian, he wanted to be a guy. He didn't. He gets to spend the rest of his life regretting it. But he can't go back to being a woman.
Third, those promoting this aren't telling the truth. One hospital freely admitted they started doing the surgeries because there was a lot of money in it. They'd say everything was reversible, but guys, c'mon! When it's gone, it's GONE. The hormones aren't reversible, either. They can put fake breasts back in, but if they do a radical hysterectomy, they've just sterilized that woman. And as my mother used to say, "If you have to lie about it, you know it's wrong."
Fourth, there's a meme out there that says it all, "Look at me!" the man with the wig says. "I am the woman now." They're trying to sell us on the idea that men make better women than women do. And where are the feminist voices in all this? Hiding, so they won't be cancelled. Being a woman isn't a costume you can put on.

It's no different than pushing back on people making the claim that the earth is flat. They are spreading ignorance to the next generation, and asking us to pretend we don't believe in science. Would you pretend the earth is flat if you were talking to a flat earther, just so you wouldn't hurt their feelings? No, it's nonsense and you know it, and you certainly wouldn't want them teaching it to your kids.

The comparison to religion is pretty bad. With the exception of Christianity, most religions are pretty pushy about their beliefs.

Well since men are kicking girls asses in sports because idiot leaders keep putting men on girls sports teams and letting men in woman's changing rooms they are forcing society's hand.