Just some thoughts on this 
I realize this race question is something of a tangent to the initial question of relativism and tolerance, but a few thoughts occurred that may link the two back together…
First off, let me commend you. You’re right in asserting that races do not, in a scientific and biological sense, exist. They also do not exist as metaphysical categories. That much is clear from twentieth century genetics and generally agreed upon by modern philosophers of race.
However, races certainly exist as a social and political reality. There is no denying this. Race is socially constructed and historically malleable (we often forget in our race-torn society that the idea of race as a scientific concept is not much older than Kant and the age of European conquest!) Race was initally conceived in religious terms (missionaries and mercenaries work awful well together) and then in scientific terms and finally in political terms. But we have to remember that saying that races do not exist as the basis for a scientific or metaphyiscal categorizational scheme does not mean that racism, prejudice and discrimination do not exist. Examples are almost superfluous, but let me just mention that the median income for a white family in America is $50,000 a year, whereas the median income for a black family in America is $29,000 a year. Race, then, clearly exists, at least as a social category.
However, this all is not to say that relativism is a dead end. Society is by its nature relativistic, since it is constantly changing. A society is never the same as itself, that is, is not merely the sum nor the average of its members.
Pure criticism is not my intention, I honestly am attempting to add something valuable to this discussion. Let me say, however, that I don’t agree with either statement here, but I do want to point out that the second assertion doesn’t even logically follow from the first.
Nothing is the same as anything else. This is getting into the question of identity, that is, whether anything is ever even the same as itself. We are reminded of Heraclitus’ river which we cannot step in twice. The second poster seems to assert that we do not even step into the same river once. This is not an inherently bad position: the universe seems to be characterized by incessant change. Our bodies and our minds are in a constant dialogue with reality, both altering the world and being altered by it. Some see this as creation, others as manipulation. I’m gonna split the knot and say it’s a little bit of both.
For example, it’s true that no two eggs are alike. But they share certain properties and perceptible features. That doesn’t mean a given feature on one egg (say ‘whiteness’ or ‘roundness’) is the same feature on two different eggs, nor to say that they both participate in a universal essence or form of ‘white’ or ‘round.’ Merely that they are handy perceptual categories. The relativism emerges here because of the way humans tend to organize reality–around properties and classes. We conceive of a property (say ‘whiteness’) or a class (say ‘eggs’) by conceiving of an exemplar of the property (a specific white thing) or an exemplary member of the class (a specific egg.) We judge other things to be a member of that class or to possess that property based on their conceptual (i.e., perceived) proximity to the exemplar of that class. So I judge these white clouds to be similar to those white eggs because, in terms of their whiteness, they are relatively the same. That doesn’t mean that the two things (clouds and eggs) ARE the same thing, nor that the properties they both possess are the same propery or possessed in common. They merely have a conceptual proximity to one another.
The point is that classes and properties are not clear-cut or agreed upon. They are, in general, given by common sense and sociolinguistic categories. That is, like society, they are relative to a culture. In this sense, even logic is relative since it emerges from language. Reason (which statements make sense) can be viewed as the ‘deep’ structure of language, even deeper than syntax and grammar, although grammar also influences the patterns of our thinking.
Happy holidays, everyone!