Most parents presuppose the principle of primortality. They start a new life from the tacit assumption that they will die well before their child since for most parents loss of a child would be the biggest catastrophe they can think of.
When deciding to procreate most parents don’t seem to be aware of the fact that for most children loss of a beloved parent is among the biggest catastrophes they can think of. At the same time most children are doomed by their parent to be still around when their parents pass away.
In order to progagate non-propagation antinatalists might talk about the immorality of the principle of primortality wherever they meet people prone to procreate.