Children aren't little seeds of goodness that just need to be set free. They are more like little seeds of anything

Toddlers, yes. If we're talking about people over the age of say, 8, then it becomes less true. By the time they are a teen, it becomes pretty false. And yet people still say that legal separation at 18 is good.

If you are merely making the argument that we should limit their exposure to things that could influence them in harmful directions, then I'd argue that this never stops being a powerful force, including for people well into adulthood and in old age.