Assume God does not exist and that evolution explains all that is. In that case absolute truth does not exist with respect to morality. A fact would still be a fact, such as the fact that I am writing with a pen upon paper, and that fact would still be true, but on moral questions of right and wrong nothing could be said to be true or false. For example, I could not state, “adultery is wrong” as a moral truth. I might say, “our society believes adultery is wrong” and perhaps that would be a true statement, but I could not make pronouncements of general moral truth. Morality thus would be relative, not absolute, and subject to change at the whim of the people.
Many try to escape this problem by saying that nothing is immoral unless it harms another person. By this they might justify sexual acts between men and men and men and animals by asserting that no one is harmed by such conduct. On the other hand they can argue that lies and thefts and murders are wrong because they do harm others. Of course, the morality of lying gets quite vague because you can often claim no one was harmed by your lie. In fact, many adulterers would claim they actually keep their spouses from hurt feelings by lying to them! Their lies are really acts of goodness, then, and moral instead of immoral! Many even go so far as to justify theft by saying that the money stolen from the person who works to support the person who refuses to work is a moral and public good.
And what of murder? Untold millions believe that murdering an unborn baby is moral because that serves the “higher” good of making the mother (or the mother’s parents or the mother’s lover) feel better about themselves. There are even those who argue that the unwanted newborn or sickly old man ought to be killed in order to reduce the stress on society. So, we see that when people abandon the principles of absolute morality, a relative morality takes its place which ultimately leads to the acceptance and promulgation of any type of behavior whatsoever. The result of such moral relativism is that we now have an entire majority political party and a new president bent upon extending all manner of civil rights to those whose acts for the first 400 years of this nation’s history were considered immoral and illegal.
I can’t argue you into believing moral truth exists. If you have convinced yourself that morality is only what man says it is, then you are, at this point in time, beyond hope. I have nothing to say to you. Go away and think about the next monster to create and your next thrill that “won’t hurt anybody.” But, if your conscience has been ever-so-slightly pricked, read the next page about belief.