@dalias I largely agree with you, though not in terms of where you imagine that intervention is justified when parenting. As a parent, I intervene in all kinds of ways, because my role with my kids is multivalent- it's a supportive role, it's an encouraging role, and it's a TEACHING role. We provide scaffolded support to our kids, naming goals, looking at the benchmarks that move our kids toward meeting them, and breaking the work toward those into pieces. One of my kids is autistic; some of those goals and benchmarks are social. Harm prevention, mostly to him, is a goal, but I "intervene," as you put it, well before harm happens.
There are certainly much more disinterested ways to parent. I don't practice them, and as someone who was in fact parented by the libertarian left (off grid and before it was cool), I don't condone them either. Hands-off harm is also harm.