"""And one of them, a lawyer, asked [Jesus] a question to test him. “Teacher, which is the great commandment in the Law?” And he said to him, “You shall love the Lord your God with all your heart and with all your soul and with all your mind. This is the great and first commandment. And a second is like it: You shall love your neighbor as yourself. On these two commandments depend all the Law and the Prophets."""
Most people have a hard enough time with those. But, you might say, what about the details? What about white lies and second donuts? That was also covered by Jesus:
"""Woe to you, scribes and Pharisees, hypocrites! For you tithe mint and dill and cumin, and have neglected the weightier matters of the law: justice and mercy and faithfulness. These you ought to have done, without neglecting the others."""
The details might seem inconsistent and controversial, but the basic morality isn't all that convoluted or up for discussion. People just don't like thinking about how everyone is bad at the fundamental stuff.
Anyway, Christian philosophy is pretty coherent even if the people aren't. And it's not clear that your expectations of consistency are required for there to be social benefits to Christian belief in particular or religious belief more generally.