And that's the hard part, that the discussion is framed as being for the benefit of the child, but my observations and experiences with helicopter parenting is that it is not really about the child, its about the parent "feeling" safer in the best of cases and about trying to appear to play out a twisted idea of what a "good" parent is in the worst cases.
The child is just the vehicle for the parent getting what they want, a feeling of security or a feeling of superiority, but that's not what they argue.
So you can't win the argument because one side is not honest. (Sure some people might be honest about it, but its usually people without children in my experience).
Maybe its about time to re frame the argument in a different manner. Maybe it would be best to argue for the emotional harm that may come to children who are not allowed to learn self sufficiency in a healthy manner.
I don't know the answer, there are surely better arguments, but you're right, fighting under the current conditions is pretty much hopeless.