Ideas are like that, paper can't blush. For a salient example, the idea of providing 12 year olds with puberty blockers and opposite sex hormones without their parents' consent didn't quite fly then, and today disagreeing with it puts you in quite a few naughty lists.
"Ideas are controversial" is no where near "ideas weren't fathomable". There are several 24 news networks that make your exact example of "unallowed opinion" as a seemingly huge percentage of their content.
But also, that's a complete strawman. No serious group I am advocates medical treatment without parental consent. There is a strong movement to let 12-year-old choose what pronouns to use in school even without parental consent.
It's more that at the time you could disagree on some things where now only one view is acceptable. The Overton window has narrowed substantially on certain subjects.