Sociopaths genuinely reject that. What you’re feeling is the gap between modern knowledge and faith: our shared moral standards were historically upheld by religious authority in a radically different world, and in rejecting religion we often mistakenly discard faith as the foundation of morality itself. Moral relativism can describe the fact that people’s values conflict without requiring us to accept all morals, but it is naive to think all moral frameworks can peacefully coexist or that universal agreement exists beyond majority consensus enforced by authority. We are fortunate that most people today agree torturing babies is wrong, but that consensus is neither inevitable nor self-sustaining, and preserving what we believe is good requires accepting uncertainty, human fallibility, and the need for shared moral authority rather than assuming morality enforces itself.