I am catholic, and while you are probably correct about the fact that the Bible has wierd stuff in it, Jesus himself never allowed murders of any kind, and his sentiments are the deciding factor in what catholics believe.
You do however make a very good point about that humans read holy texts with the goal of making them fit their own lines of thought. And it is also true that some things (the abortion issue for example) has been decided by church leaders, and not by God. That said, those leaders have tried to do what they think fits with what Jesus would have wanted. So the goal is to have morality madeby God, but humans are humans, and thus open to fail.