I was trying to get at this the other day, but Archbishop Chaput puts it more deftly than I:
Relativism is now the civil religion and public philosophy of the West. Again, the arguments made for this viewpoint can seem persuasive. Given the pluralism of the modern world, it might seem to make sense that society should want to affirm that no one individual or group has a monopoly on truth; that what one person considers to be good and desirable another may not; and that all cultures and religions should be respected as equally valid.
In practice, however, we see that without a belief in fixed moral principles and transcendent truths, our political institutions and language become instruments in the service of a new barbarism. In the name of tolerance we come to tolerate the cruelest intolerance; respect for other cultures comes to dictate disparagement of our own; the teaching of “live and let live” justifies the strong living at the expense of the weak.
This is from his speech in Slovakia. The entire piece, which is well-worth your time, can be found here: