You’re talking in circles. I asked you why certain actions are wrong, you said empathy. When I asked you why empathy is good, you said because it stabilizes society. When I asked you why it matters whether society is stable, you say empathy.
But, I will answer your question. Just because human beings fail to live up to moral absolutes, (what Christianity calls sin) does not mean they don’t exist. Like in Olympic gymnastics, very few score a perfect 10, but that doesn’t mean a perfect 10 doesn’t exist. Most people know it is wrong to lie, steal, kill, etc, yet, we’ve all done those things at one time or another (not everyone has killed, but you get the point).
Just because someone is a Christian does not make them automatically perfect. Besides, there are those who may have a distorted understanding of the faith. They may be blinded by their upbringing or culture. And there are those who are Christians in name only. They may call themselves Christian and go to church every Sunday, but they’re simply exploiting the name for their own purposes- Jesus warned us there would be people like that.