Argument that subjectivism (individual relativism) is mistaken (pp. 14-17).

Argument that that ethical relativism has unacceptable or "absurd" consequences (p.16) (e.g., Mother Theresa is no better than Hitler).

Argument that ethical relativism is false (p. 17). 

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. And social reformers like Jesus Christ and Martin Luther King Jr. are immoral.

But we make moral progress in limiting harm to children, and not all social reformers are immoral.

.·. Ethical relativism is false.

And it is self-refuting: (p. 18)

The ethical relativist thinks that relativism holds everywhere (in every culture).

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 some cultures do not endorse ethical relativism. 

So those cultures should not endorse ethical relativism.

(Ethical relativism tells everyone to be an ethical relativist, but it also tells some people not to be an ethical relativist.)

And any argument that relativism is good because it is tolerant is also self-refuting: (p. 18).

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).

So ethical relativism tells us that no cultural system is better than any other, while also telling us that some are better than others.

The only way to consistently praise tolerance is to reject relativism.