I've related the anecdote before here of a conversation I had with a very liberal friend of mine. I'd asked my friend first if he believed it was possible for one culture to be objectively superior to another, to which he emphatically replied "no". I then asked him if he believed in the existence of universal rights, those rights to which all human beings are unconditionally entitled. He saw the contradiction and said I'd "worked him into a corner". Indeed.
We're exhorted over and over again to "celebrate" all cultures and hold them in equal esteem. Yet in certain regions of Afghanistan, it's an accepted practice for grown men to take young boys as sexual playthings. In Saudi culture, women have a social standing roughly equivalent to that of breeding stock. In parts of Pakistan and elsewhere, women are routinely stoned as adulteresses for the crime of being raped. In Iran, homosexuals are hanged in public. And hardly a week goes by without a story in the news of a Muslim male killing a female family member to restore the family's honor.
Are these just cultural oddities that are to be laughed off so we can get on with the more lofty goal of celebrating those cultures? No. To claim that all cultures are on an equal moral footing is to deny the existence of universal human rights.
The logic here is simple and unassailable. If one believes in such universal rights then one cannot believe that all cultures are equal and worthy of being "celebrated". To believe both betrays not just a complete failure of logic but a despicable moral dishonesty.