I am certainly not someone well versed in the area of psychology, as I have only a lay understanding of many if not most aspects of it. But when you say there is no proof of empathy being the source of altruism and the lack thereof being psychopathy, is that your interpretation, or more of a fact? I only ask to understand because, having not studied it really at all myself, psychopathy, in my mind, has always carried that basic definition- that it was someone who lacked empathy, amongst other indicators. At some point I do recall reading something about psychopaths that indicated that they were able to 'act' as if they had empathy in order to gain something, but that, in reality, they did not 'feel' empathy. I don't recall where I had read that as it was a long time ago so I have no idea if it was a reliable or factual source at this point.

I would agree that yes, in many cases, externally perceived altruistic behaviours may not in fact be altruistic for as you said they me be self-righteous or have some type of ulterior motive - which kind of seems to lend to how a psychopath may use 'acting' altruistic right?