It was the sin of Roman Catholicism to presume to have a privileged perspective on human nature, and if you disagreed with them, you got burnt at the stake. So no thanks, let's not talk about some ivory tower perspective on "human nature" shall we? We all know where that goes.
Ethics in my church literally flows from the cup of Christ's blood and the broken bread we share as the body of Christ. It is a completely different perspective from what you are talking about. Community is at the heart of ethics, and we see that signified in the kinds of sacraments and examples Christ patterned for us.
One of the most moving experiences I had years ago was attending a foot washing on Maundy Thursday and washing a stranger's feet (It's the basis of "ubi caritas", since that hymn is frequently sung then). This is a perfect example of Jesus' pedagogy of ethics. We have to become intimate with the stranger in order to serve the stranger. The carnality of their lives is the very stuff we must be open to accepting if we are to serve them.