Maybe this is just a nit, but calling someone a sociopath isn't necessarily calling them 'not a true human being,' so I wouldn't put words into his/her mouth. Saying, "You can't argue with a sociopath," could simply mean: "Any argument that I could pose, couldn't be rightly understood by the other party, so I would be wasting my time."
Wonderful ad-hominem attack: "I can't make a convincing argument, therefore I'm going to write the other party off as not a true human being".
I salute you.