

I’d say there’s a difference between assessing people’s fitness to have children, and their fitness to raise children. The latter is a lot less eugenics-related, and clearly necessary in some form to protect children from being abused by their parents.
Though of course it isn’t always done perfectly or even well.
I guess that’s the joke - this is so stupid and obviously won’t work, but that perspective is subverted when it turns out to actually work, causing humour.
I quite like it.