I agree. Think of how often the bad/evil characters in stories, all the way back to the Bible, are depicted as snakes or dragons or reptiles. You'll see it all the time in movies.

It's because sociopaths/psychopaths, like reptiles, have no empathy and therefore no conscience. These humans aren't literally reptiles, but they have exactly the same sort of emotional range as the most dangerous of snakes, giant lizards, and crocodiles. That's why these people act the way they do.