"If relativism is true, then all moral categories are meaningless. Any attempt at moral discourse is reduced to incoherence. Therefore, the only course of action truly consistent with moral relativism is complete silence. If you view all morality as relative and you're consistent, you can't ever make a moral recommendation."
"A person can wax eloquent with you in a discussion on moral relativism, but he will complain when somebody cuts in front of him in line. He'll object to the unfair treatment he gets at work and denounce injustice in the legal system. He'll criticize crooked politicians who betray the public trust and condemn intolerant fundamentalists who force their moral views on others. Yet each of these objections is a meaningless concept in the twisted world of moral relativism." Greg Koukl
Regarding Relativism and the Problem of Evil:
"The approach many relativists take at this point is confused. First, they say that the Holocaust was evil and ask why God would allow such depravity? Later, when the tables turn and their own behavior is in question, they argue that morality is merely a matter of opinion. This reduces their earlier objection to: "How could a good God allow things that are contrary to my opinion?" or, to put it more bluntly, "I can't believe in the existence of a God who would disagree with me."" Greg Koukl