What was Radcliffe doing at age 11? Working.
He was exposed to adulthood at an extremely early age. His experience of reality and ability to make decisions is warped. Probably because he got lucky and had a good team around him protecting him, which is the exception rather than the rule for child stars.
So I can understand why he would have this warped notion that children have the ability to make these decisions.
But that neglects the issue that a lot of children are way more immature and vulnerable than he ever was and aren't necessarily surrounded by people who have their best interests at heart.
This also doesn't cover all the ethical reasons or medical harm results for raising concerns. He has just instantly dismissed them saying that doesn't matter, the only thing that matters is children get what they want. Trouble is what they think they want and the reality of what's on offer don't match.
This is all a reflection of his childhood and having to grow up very early in a very protected environment though. I hope he has a child who suddenly makes him reconsider a lot of this...