I feel like that’s a hyperbolic take. Outside forces injecting chaos into the internal workings of a family are about as bad as things can get for a growing child. What’s the problem with deferring sexual issues to adulthood when you’re more mature?
What makes you think that a marriage between two people gives them absolute knowledge how to raise a child in an optimal way?
That’s part of the deal isn’t it. The government can’t decide and mandate what the optimal way to raise a child is outside of certain aspects like schooling, corporal punishment, age of consent etc.
What makes schooling, corporal punishment, age of consent, and - as discussed here - control over online communication acceptable government interventions into an otherwise wise, benevolent and self-sufficient family?
The problem is that those sexual issues arise for the individual almost as soon as they begin to experience puberty. You can’t make teens to ignore their sexuality for 6+ years. It simply will not work, it never has, it never will.