" it takes an especially cold personality to be able to inflict pain and suffering on another - no matter how you may perceive them as deserving of it."
I agree with pretty much everything you've said, Andy, apart from this. There's more than enough evidence (mostly from social psychology but I'd be surprised if there wasn't some investigation into it from neuroscience as well) suggesting that even average, normal people can be gotten to willingly do terrible things in the right circumstances or with the right emotional setup. So I disagree - I think, accepting the difficulty of generalisations, many of the self-righteous you refer to would willingly throw the switch. How they'd feel about it after, on the other hand, might be a different question...
Like many of my posts, I do worry about this seeming pedantic, but it's really not intended that way at all - it makes an important difference to the kind of discussion we're having.