That's deflection. The point is that Monty is actually correct in that you can find a scientific basis for pretty much everything if you look hard enough.
Although quite why that is relevant to anything I have now forgotten.
F*ck me, what was this thread about in the first place?
It's not deflection. Such a purely utilitarian analysis would, for instance, almost certainly conclude that disabled children would be best off being euthanised. After all, they will only ever be a drain and never contribute. Do we do that? Of course not. Why? Because our belief system (which, whether m likes it or not, is still based on Judaeo-Christian lines) tells us that to do so would be abhorrent.
However, my only point is that, while I am intensely glad that that is how we do things, trying to claim the reasoning behind it is scientific is nonsense.
Believe it or not, I'm sure you could come up with a measurable approach to proving that society would be better off without euthanasia.
However I agree with your second point. The way society has evolved is largely organic, without any pre-thought whatsoever. The fact that so much of it is scientifically justifiable is because of the number of variations and iterations that have occurred over time. We may not have planned it, but we do eventually get things right, us humans.