As a child, I might well have argued that.

But now, I appreciate that children are easily manipulated. So while it's possible that some particular child might have freely chosen to have sex with some particular adult, there's no way to determine that. And so the rule must be that children can't reliably consent.

Still, people have the right to say whatever they like. And people also have the right to vilify them for it. And so, recursively, ad infinitum.