I still can't bring myself to find it excusable.
It's not an excuse, it is an explanation. These behaviors are not simply because
There are psychology terms for people who are numb to human cost, and they're generally synonymous with "not capable of thinking in terms of morality".
No, they aren't. You're thinking of psychopaths, but our governments aren't full of psychopaths. It's impossible, both statistically and practically. You have to think of these things from the viewpoints of the people who do them if you are ever to understand why they happen.
There's too much debate as to what constitutes psychopathy, proper terminology (I prefer sociopath myself), whether it deserves to be broken out into categories, etc to properly dig into this. Ability to remain affable in the face of the most extreme moral accusations, egocentrism, and lack of remorse for one's actions are all defining features, regardless. This condition is actually not at all uncommon among the general population, and I'm pretty sure there have been studies showing that they are very, very good at populating the upper levels of authoritative hierarchies.
I do look at things from their point of view, as much as is possible for me to do so. The motivation was to stop "the threat of a good example". Kissinger, and others involved, were afraid that the legitimacy of their ruling class would be damaged by an opposing ideology actually achieving positive social change, so they stepped in to disrupt peaceful attempts at progress with violence. If that isn't sociopathy in action, I don't know what is, and I hold that righteous indignation followed by steps taken to prevent those and similar people from causing further harm is the correct reaction.