As a parent, I'm of two minds on this.
Yes, I agree that suppressing a child's gender identity and orientation is harmful and could be classified as child abuse.
However, parents already deal with the nightmare that any little thing, especially a false accusation, could end up with child protective services being called and severe consequences. Kids being taken away is not really easy on a parent, and some states are absolutely ruthless. Ask any parent who has dealt with NJ DCF/DYFS. They have virtually unlimited power, and even when they are clearly wrong, court battles can sometimes only result in a partial resolution. What's more, unaccountable bureaucrats run the show, and they don't seem like they care about families.
For example, a friend of mine posted a picture (on facebook) of his son with a rifle in his hand. It was unloaded and he was supervised by his father who is a firearm safety instructor and has a federal firearm dealer's license (which requires extensive background checks). The guns are locked up at home in a safe otherwise. But someone saw this, called the cops and DCF got involved. They came to his house and wanted to search the home. He refused under the 4th and 5th amendment. The cops and DCF tried to lie their way in but he called his attorney (also a friend of mine) and eventually they had to leave because they couldn't get a warrant.
As for kids and guns - people have their opinions, but in reality kids have been handling firearms for a darn long time. Kids as young as 10 years old can get a hunting license even in the most progressive of states (like NJ), and teenagers involved in scouting and other activities do rifle target shooting for merit badges and similar.
Another case is Justina Pelletier. She was the teen who was being treated for mitochondrial disease, but a hospital in Boston thought she was mentally ill and faking it, so the state took her, stopped her treatment and she grew progressively worse. Eventually the parents were able to get her back, but not after media attention and public outcry.
So I'm not entirely convinced that something like letting the Government seize kids from transphobic and homophobic households is the answer.
What I do support is the banning of so-called conversion therapy. I also support access to transgender hormone therapy like how birth control for teens is handled in some states. Let trans teens get puberty blockers and access to counseling via the school system with optional parental notification, not permission.
But I think the biggest weapon against this is bringing people over to our side. It will be a slow process and not 100% but it has to be done that way. That is the best way. I am firm believer in parents parenting their kids, not the state.
Otherwise what will happen is even more child abuse. I think that if we tighten the screws on parents, truly abusive parents will take drastic action like hiding their kids from society with home schooling, or shipping them off to relatives in other states who have looser laws against abuse.