That might be the case. I don't see why it's not possible some people just don't have whatever it is that causes empathy, rather than it being a complete spectrum.
Everyone acts sociopathic to strangers. Empathy can't be felt towards an abstract concept. A normal person is capable of feeling empathy. They could get to know the person or even just learn a little about them and imagine them being in their place. A true sociopath wouldn't be able to do that.
My point is that we don't know that. We're taking that on authority. I'm questioning the basic premise that there are a significant number of people who don't feel any empathy. More than people who congenitally don't perceive pain, say.
None of the actions / behaviours I've seen that are attributed to psychopaths require a total absence of empathy. Instead, just extreme selfishness, impulsivity (delay connecting actions to consequences) and a strong ability to rationalize one's own actions post-facto.
Everyone acts sociopathic to strangers. Empathy can't be felt towards an abstract concept. A normal person is capable of feeling empathy. They could get to know the person or even just learn a little about them and imagine them being in their place. A true sociopath wouldn't be able to do that.