If slavery is not wrong, nothing is wrong.

--Abraham Lincoln 

Ethical relativism says "that what is right is what the culture says is right."

In contrast, absolutism holds that some "absolutes" (some fixed principles) are true apart from their being endorsed by any individual or group.

The key distinction made by the absolutist but not the relativist (where "X" is a placeholder for whatever is at issue):

Thinking X is right vs. X actually being right.

If we are not tempted by nihilism or subjectivism, then showing relativism to be mistaken is good reason to adopt absolutism. (But notice that this does not tell us which type of absolutism to endorse.)

      Argument that subjectivism (individual relativism) is “muddled."

Argument that that ethical relativism has the unacceptable consequence of invalidating all moral reflection and criticism. (e.g., social reformers are always immoral, & there is no moral progress).

First version of the argument:

If every cultural system is valid, then none is better or worse than any other (there is no non-ethnocentric reason to prefer one to any other).

But even relativists believe that some cultures are worse than others (harshly ethnocentric Euroamerican practices are often singled out as worse than the "gentle" ethnocentrisms of most tribal peoples). AND we have non-ethnocentric reasons to condemn these practices.

.·. Ethical relativism is false.

Second version of the argument: 

If every cultural system is valid, then none is better or worse than any other (there is no non-ethnocentric reason to prefer one to any other). But then random torture of small children is perfectly right for no other reason that that it is believed right by the culture that tortures the children. 

But believing this behavior to be right does not make it right.

And this standard makes every unpopular moral reformer immoral.

.·. Ethical relativism is false.

THREE COMPLICATIONS:

Also, ethical relativism faces three serious problems in explaining its position.

1. If group consensus is the moral standard, then small changes in group opinion can change the moral status of anything. We will have constant "moral flip-flops."
2. What blocks small, cohesive groups and subcultures from claiming moral immunity from the standards of the surrounding culture?
3. Everyone belongs to multiple cultural groups. These groups often have competing views of what is moral. Therefore someone's behavior will often be simultaneously right and wrong.