[Serious] Good vs Evil

[Smaug]

P. S. speaking of 'why it's hard to comprehend'... I guess it's hard to settle with 'Good' and 'Evil' being relative because it makes the world seem much more brutal. No absolute justice, no higher help etc.

Plenty of atheists (such as myself) are moral realists. Why do I reject moral relativism? Because the arguments for relativism are not logically sound. And that's a problem.

Consider again the example of the Greeks and Callatians. The Greeks

believed it was wrong to eat the dead; the Callatians believed it was
right. Does it follow, from the mere fact that they disagreed, that there is
no objective truth in the matter? No, it does not follow; for it could be that
the practice was objectively right (or wrong) and that one or the other of
them was simply mistaken.
To make the point clearer, consider a different matter In some societies,
people believe the earth is flat In other societies, such as our own,
people believe the earth is (roughly) spherical. Does it follow, from the
mere fact that people disagree, that there is no "objective truth" in
geography?

Stricktly speaking, by considering this statement you cannot derive that there is any objective truth about moral absolutes either. The only thing you can firmly say is that there are conflicting moral codes. On the other hand, relativistic hypothesis works well enaugh in explaining moral behaviour without invoking moral absolutes at all. Rejecting moral relativism on the grounds of the aforementioned arguement is like rejecting Einstein's Relativity on the grounds that he did not strictly disprove the existence of an absolute reference frame.

If you feel like having a 'moral constant' then you can reason along this line: certain set of rules of social interaction allow societies _and_ most of their members to thrive (or at least live a bearable life). Such a set of rules may be considered 'optimal' at least for a very generalized case.