However emotion stems from ones sense of morals and deep rooted beliefs. Anger is especially linked to one's morals. Anger for example is stems from a sense of injustice. Take the scenario of the mugging, if you didn't get hurt, didn't lose more than a few dollars(no big loss), why should you get angry unless you had some moral sense that one shouldn't steal from you.
If one truly follows moral relativism, one can condone Hitler's holocaust of the Jews, Stalin's purges of millions of people. Since one can not pass any moral judgement, one has to concede that there is nothing inherently "wrong" with such actions.
Taking moral relativism to the extreme, one could argue that there should be no laws, since laws impose one's view of morals upon society. (For example, how can one condemn murder if one believes that one can not impose any type of moral judgement?) Obviously such a society could never exist or survive, hence moral relativism is a failed philosophy.
When it comes down to it, moral relativism is a contradictory philosophy. If all moral views are equally valid, then two contradicting moral views must be equally valid. However, logically two moral views can not both be correct, leading to a prardox. This is one of the big faults of the moral relativism philosophy.
Although different culturals haves different views of right and wrong behavior, no human can truly follow moral relativism. All humans have some deep rooted sense of morals. Even though some people are more open minded, even the most "open minded" and tolerant person has to draw the line somewhere.
(sorry for the philosophical rant)
