Comment by anonymars

You are absolutely missing the point of what he is saying. Once your kid gets to a certain age, you are no longer able to control them. Regardless of the reason (nature vs nurture), if your kid starts going down a bad path, you the parent are unable to rein them in.

The context was that he watched his stepson get into drugs, and was unable to force him into rehab. If the son left, the parents could not coerce him into staying.

And so his son died of a drug overdose. (https://news.ycombinator.com/item?id=46604020)

So if you are in that position, and your kid gets into drugs, and there is nothing you can do about it, what would you do as a good parent?

Now apply the same thing to if you think your kid is becoming a danger to others.

His full statement was that if we collectively reject the premise of restricting someone's (the child in question) bodily autonomy (by committing them), the argument is the only two options that remain are to watch helplessly or kill your kid. Obviously he is not seriously advocating the latter any more than Jonathan Swift was truly advocating for eating them.