Well, Billy and Bob both possess their values naturally, they were born with and without empathy as a result of biological processes in their brains, respectively, as I stated in my hypothetical. And stating that it's an objective fact that people have a certain value doesn't have an impact on the objectivity of that value. I mean, I feel bored right now. It's an objective fact that I feel bored, but that doesn't make my feeling objective. So all you have left is "typical". So it does seem to be the case that you think Billy is correct because there are more people that feel like him than Bob.
It's a fact that some humans lack empathy completely and have no value for human life. Why are they incorrect? Simply because most other people do? Other than your appeal to popularity, everything you keep saying applies to Bob just as much as it applies to Billy.
ETA Why are you putting "correct" in scare quotes? And "correctness"? As if you might ask: 2+2=4, is that "correct"? There are varying degrees of accuracy, there are not varying degrees of "correctness" that are open to opinion. If it's open to opinion, then it has nothing to do with being correct.