I define sanity as acting in a logical manner. Not doing something out of guilt, empathy or because it just feels “wrong” is, strictly speaking, not logical.
To our credit, most humans are not purely logical creatures. Sociopaths are.
I admit that I cannot explain serial killers.
But most sociopaths don’t kill for the sake of killing; they want what we all want: money, power, respect. It’s just that they’re not held back from achieving these things by the same psychological restrictions (“insanities”) that we are.
A sociopath is, in essence, a parasite on a functional human society - they take advantage of social interactions without taking part in them. A society consisting purely of sociopaths obviously wouldn’t last long.
I think you may want to elaborate a little more. To me it seems that that is exactly what happens in a communal species. If the group is capable of looking out for one another, it becomes advantageous for the individual to join the group, and thus need to do things that are good for the group. Those that do not are more vulnerable, and become selected against. This would still seem to be a form of natural selection.
Not sure about Clinton or Obama, but Tony Blair certainly seems to be somewhere on the spectrum of personality disorders, and he is superficially charming and a natural liar.
See this report. Either he genuinely believes what he says (even if it is wrong) or is a blatant liar, I go with the latter myself.