That's an interesting article, but I find the conclusion peculiar. So there's no good scientific evidence that corporal punishment helps children in the long run, and the best available evidence links it to worse outcomes rather than better ones, but because we can't do stuff like double-blinded studies with control groups, "bans on smacking have got far ahead of the evidence, and should be actively opposed until the science is much more solid"?

That's not the conclusion I'd draw from that body of evidence.

One point is that "the best available evidence" is of very poor quality, with known obvious confounds and mishandling of longitudinal data. (For example, Robert Larzelere argues that by the methods used, grounding children, and giving them therapy, also harms them: (https://link.springer.com/content/pdf/10.1186/1471-2431-10-1...) Another point is that parents may be well placed to know what is best for their children - better than "experts".

Seems there actually is a fair amount of research pointing to prohibiting corporal punishment for kids leads to better mental health, lower suicide rate, etc. and it does seem like a no-brainer to me that less violence leads to more stable individuals, and a more stable and happy society in general. In medieval times there was a lot of physical punishment, and society was violent, dangerous and unhappy compared to now. Singapore may be modern in many respects, but in this area, they're a bit of a backwater.

I interpret their argument differently. We know that bullying leads to harmful outcomes. We know that punishment reduces the frequency of undesirable behaviour. So we know that this policy will lead to an aggregate reduction in harm. The question is whether it could lead to some degree of harm to the bully. In the absence of compelling evidence of that, the policy itself seems merited.

For the record, bullying is a complex problem to solve, and no nation or policy or tactic has the silver bullet.