So just what does it mean to be a "centrist"? To people who don't care much about politics, it may just seem like centrists are a third team between the right and the left, doing their best to advance their own interests, just as everyone else does. But if you believe political beliefs matter, and that politics is where our competing visions of the world come to fruition or are defeated, then centrism is the most cynical ideology of all, one utterly devoid of substance.
That isn't to say that one has to be a conservative or a progressive to be principled. Libertarians are among the most politically principled people you'll ever encounter, and their views don't line up neatly on the left-right axis that defines much of our politics. But unlike libertarianism -- or conservatism, or progressivism -- centrism defines itself not by fundamental principles or a particular view of the way the world works, but simply by what other people are thinking. The centrist isn't sure what he believes until you tell him what the left and the right believe. Only then does he know where he should put himself.
With all this talk about what is conservative and what is liberal, it's worth pointing out that centrism isn't really an ideology in and of itself. It's true that centrism is an ideology of relativism. It's really odd, then that someone would proudly call oneself a "centrist" when there is no coherent ideology that goes with that. In the end, the center is what is left over after the right and the left have staked out their positions. It is a remnant of an ideology, not one itself.