I grew up in the Bible Belt and churches in my hometown would put up homophobic messages on those outdoor notice boards that you see as you drive by. Not every single one, but not none of them, either. This was going on until the late 2000s at least, I’ve heard it’s marginally improved.

Yeah, it's the parents. Their views are passed on with every minute in the household. Children absorb.

It's not shitty parenting. Kids at a certain age just don't take correction from people who they don't feel have a right to correct them. Sometimes that person is no one. My kid refuses to believe the sun is not a planet. She will argue until she's blue in the face. She has argued that she's a boy. Later that she's a girl. She misgendered people all the time and wasn't open to correction from anyone including me for a while. You think, "call people what they want to be called" is an easy lesson to teach. It is not. It took over a year to make it stick. Kids are just dicks sometimes.