The major religions have more resources for productive debate than multiculturalism.
But while I certainly didn't want to get into a shouting match about God's existence in the doctor's office, or wait for treatment until everyone had agreed on how to live, I see no reason why we should ignore our differences altogether. Some advocates of multiculturalism ask us to celebrate, rather than just tolerate, diversity, as if our differences weren't a reason for disagreement in the first place, but something good and beautiful - a multicultural "mosaic"! Others argue that our moral, religious, and philosophical convictions shouldn't leave the private sphere. A good example is French laïcité: you are a citoyen in public and a Jew, Christian, or Muslim at home. Both models try to remove our reasons for objecting to beliefs and values we don't share - one tries to remove them altogether, the other tries at least to keep them out of sight. A culture of debate, on the other hand, allows us to engage our differences in a way that is serious, yet respectful and mutually beneficial.
Clearly this is right. I've talked before about how some elements of liberalism stress a kind of minimal coexistence, a stance that could sap the life and vitality out of any kind of human flourishing or society.
The rich philosophical literatures we find in Judaism, Christianity, and Islam, as well as in the Eastern religious traditions offer plenty of resources for a culture of debate. The privatization of moral, religious, and philosophical views in liberal democracies and the cultural relativism that often underlies Western multicultural agendas are a much greater obstacle to a culture of debate than religion.
Instead, the point is to conduct debates in a certain way, with certain virtues of open-mindedness. But also some respect for truth and a willingness to think some cultures and views are mistaken.
Quebec is interesting in this respect, with deep controversies over accommodation of immigrants and language. The "mosaic" view the author refers to is actually absolute orthodoxy in English-speaking Canada, which likes to contrast itself to the US "melting pot" model. That doesn't fly in Quebec. Sensitivity about the maintenance of Francophone culture and the French language means the province is much more skeptical of multiculturalism than Anglophone Canada."Interculturalism" is preferred. French speakers think of themselves as a tiny minority in a vast ocean of English-speaking North America. Multiculturalism was invented by Pierre Trudeau in 1971 largely as a way to minimize and displace differences between English and French- speaking Canada.
The issue remains controversial, so much so there was a major commission report in 2008, partly led by famous multicultural philosopher Charles Taylor. And the current Quebec election campaign is marked by continuing argument about whether to have a crucifix in the provincial assembly.
Ironically, the main reason social attitude surveys differ between the US and Canada is Quebec tends to be far more left-wing on most issues than the rest of Canada, and skews the averages.