I agree that tolerance is often a good thing, but I'm not sure that that is the question here.

I think we are asking whether a moral rule requiring tolerance of other values and ways of life logically follows from the meta-theory of ethical relativism. I don't think it does. Let me approach this two different ways:

• First, we all agree that there is a lot of moral diversity in the world. But this is just a statement of fact. There is no way to derive a moral rule like "We should be tolerant of diverse moral values" or "We should not interfere with other cultures" from a simple anthropological fact.

• Second, let's focus on the "equal validity" or "equal truth" of some contradictory judgments. This is a meta-ethical thesis about moral judgments. How are we supposed to derive a moral judgment like "We should be tolerant of diverse moral values" or "We should not interfere with other cultures" from a meta-ethical thesis?

I don't see how we can derive any moral rule from either the fact of diversity or the meta-ethical thesis about equal validity. This doesn't apply just to tolerance, it applies to any moral rule.