There are quite often two extreme reactions when it comes to cultural variation.
– To assert that cultural differences are to a great extent incommensurable. The more extreme caricatures of this position fall into the class of cultural relativism.
– To assert that cultural differences are fundamentally superficial, and that all differences are easily resolvable through reconciliations of semantic confusions. The idea that all religions “believe in the same God” falls into this category.
Both have grains of truth, but the deeper reality which we are confronted with is that the topography of human culture is not flat, nor is it randomly rugged. There are broad cross-cultural patterns over time & space which exhibit surprising synchrony. To give an explicit example, between the years 1000 BC and AD a wide range of human societies shifted away from the time immemorial practice of human sacrifice. The shift occurred in the West and the ancient Far East. Both the Classical Greeks and Chinese have memories of human sacrifice in their mythologies, and the archaeology and textual evidence does confirm this practice in both societies in the late Bronze Age. The Romans, savage as they may be in our eyes, nevertheless were shocked by human sacrifice among the Carthaginians and Celts. In India the blood rites of the Vedic Aryan religion gave way to the more philosophically sophisticated Dharmic religious ecology.
But there are deep differences today as well. There have been several attempts to introduce Christianity to China. In all of these attempts there was a repeated problem insofar as Chinese culture did not have a category in which to place an exclusive monotheistic religion aside from Islam. Islam to a great extent had been ethnicized in China proper. So Christianity was often perceived to be a new sect of Buddhism (Pure Land), and the Virgin Mary would be revered along with Guanyin in the normal syncretistic course of Chinese religious practice. This does not mean that the Chinese could not never comprehend religious exclusivism and Christianity. A minority of modern Chinese are Christians of conventional form, and an even larger minority of South Koreans are Christian. Rather, the repeated similar reaction of East Asians to exclusive Western religion indicates that there are common presuppositions in these societies which are at tension with the presuppositions of Western religion, which is not only exclusive, but monopolistic in intent, and simultaneously supernatural and philosophical.
In the modern era the earlier patterns of simultaneous difference and concurrence persist. There are some aspects of the Western liberal project which have obtained nearly universal acknowledgement in terms of their legitimacy. The necessity of rooting politics in an ultimate democratic principle. The abhorrence of involuntary human bondage. I give these two examples because the “Western” view is now nearly the universal view. Even societies and cultures which are not democratic give a hypocritical nod to the democratic principle; e.g., the Democratic People’s Republic of Korea. And even Muslim societies where broad swaths of the population may agree in principle in the God-mandated validity of slavery, such as Saudi Arabia, are not going to violate the modern ban on this practice. At least openly. But I offer these two examples also because in the pre-modern period the fundamental legitimacy of democracy and the objectionable nature of slavery would have seemed laughable propositions in almost all societies and cultures. This illustrates the universal principle of human values which bind us together at a given time across societies, though they may separate us from our ancestors.
But there are other planks of Western democratic liberalism which are more controversial. The idea that a human being could be killed for blaspheming against the gods seems ridiculous, medieval, and eminently barbaric, to most Westerners. In East Asia it is in the class of “not even wrong,” because those societies are not so rooted in a specific organized superstition which demands public deferences. But the idea of blasphemy is also a human universal, and the last man killed for atheism in the British Isles was executed in 1700. A mere ~300 years in the past. It is well and fine to express shock at the reaction of Pakistanis to a political assassination motivated by love for blasphemy laws, but the shock is predicated on the mistaken idea that these people share our presuppositions. They don’t. Westerners in 1700 probably wouldn’t have shared our presuppositions either.
The Western attachment to free expression has its own limits. Most European states, and Canada, ban wide swaths of speech. Even in the USA narrow classes of speech are banned. Many Muslims obviously view insults toward their superstitions in the same manner. This seems strange to many Westerners, but it is probably more the human norm. To the primitive mind gods are real beings, and they have power to affect this world. Even “conservative” and “traditional” Western religion has to some extent been purged of the magical and demon-haunted in a way that Islamic religion obviously has not (the same can be said of South Asian, African, and Latin American societies, but they are less characterized by a brutal religious monopoly). These societies are at a different stage of development, and perhaps are on a different track altogether. They are different, and there is a layer of deep emotional and intuitive incommensurability.
In terms of the implications, I think we need to keep in mind these differences, and similarities, when framing international global institutions. The set of universal and core values are thin. The set of civilizational specific values are thicker. We should not confuse the two. I also believe that the chasm of thick values makes a robust multiculturalist project ultimately doomed to failure. The only way multiculturalism can thrive is by making cultural differences into trivialities. Focusing on food, dance, and dress, as they did in the former Soviet Union.