The Golden Rule is pretty self-explanatory and is a solid foundation for moral behavior. I don't rape, murder, steal, etc., not because I'm afraid of God's wrath, or that of the police -- it's because I wouldn't want those things to happen to me or my loved ones and am able to understand that others feel this way too.
Meanwhile, that moral absolutism give license to kill people for blasphemy. And there's plenty more horrible things that are done to others because God said so.
Everybody's entitled to have their own relationship with God (even as an atheist I do in my own way), and I acknowledge that there's plenty of good that comes from people practicing their faith, but that is easily countered by very bad stuff that is morally justified by their interpretations of scripture.
And this concern is everybody's -- because there's ongoing efforts to make the US into a theocracy and that would be a very bad thing.