In discussions with atheists, I always find it both amusing and puzzling that they almost never fail to make statements such as "I believe human sacrifice is wrong" or "in my opinion the Canaanite genocide was wrong". Now either they are trying to persuade me that such things are objectively wrong (in which case they have just denied their atheism) or in the unlikely event that they are really just giving me a personal opinion, I can only answer, "that's nice, good for you. Good luck with that". For if it is merely a personal opinion among millions of others, the statement is about as meaningful as the most absurd trifle.
A personal opinion about right and wrong has zero authority ... so why talk about it so often and passionately if you did not think it is truly right or wrong? if all is relative, as you claim, then someone else's opinion is not only just as valid, but to be celebrated. There is no "better" or "worse", "right" or "wrong" opinion in a relativistic world ... for something to be "better" would imply there was an objective standard of truth he/she was measuring it by.
A frequent visitor who is an atheist replied to this comment by challenging me with the following incoherent rambling:
"If I say, 'A cooked egg is better than a raw egg. Would you reply, "You stated an opinion about eggs. You must believe in an objective standard of egg quality."