The way I see it, by denying their offspring a better chance of survival they simply prove/propagate the Darwinian theory which they no doubt despise.

It almost seems a shame to stop them. I said, "almost"... When they do the same for grown-ups we do not prosecute them, after all, do we? But I accept that there is material difference when the victim is a child, who may not know better and cannot defend him/herself.