It seems pretty clear that some extent of our personality, disposition, tendencies, the way we process information and the way we react is based on how we are wired when we are born. The extreme example would be sociopaths or the insane, but we can see it in "normal" cases too. From ADHD and bipolar disorder to being an introvert or an extrovert, we can see physiological differences in the brain and we know people process the world differently. Wouldn't that naturally impact the way individuals determine their values and approach moral reasoning?
Do you think it is possible to have moral reasoning that taps into something pure and objective? Is that what the Church is for? And even if we are flawed and can't reach it, which explains the individual variation in people and fits with religious teaching, you still believe it is out there? One absolute truth?
I don't see it. I think people are different (genetically different) and as a result of that (and experience) they will have differences in moral reasoning. So genetics impacts moral reasoning. We have some persistent themes but lots of variation around the mean, lots of different conclusions, and a whole lot of justifications for things that would otherwise be considered immoral.