Found this post in Outer/Pol/. Thought it was quite good:
I don't believe that people with widely varying cultures cannot live together peacefully in society over the long term, especially when the proportion of one demographic slowly eclipses that of the other. We see this everywhere across the West, especially in Europe. Minority races, cultures, or religions form insular, self-segregated communities because they fundamentally do not identify with the culture of the wider community.
I don't blame them. If I was born in Libya, for example, I would rather spend my time around Westerners because I don't identify with Libyan culture, and Islamic values. Indeed, I would bring my children up with certain values, and ensure they read the great works of literature and philosophy that has emerged from Europe, and later the United States.
Provided population sizes are small, it's not an enormous problem. Yes, you may get a few people rebelling against the society, committing petty crime and the like, but mostly they will stick to their communities, and leave them to go to work, and then come back. The issue is that not only do they teach their children the values of their respective cultures, oftentimes the sizes of these communities grow.
Take Islam in the UK. Originally a minute proportion of the population, Muslims now make up potentially 4-8% of that country's people. As the population has grown, not only has their radicalism and lack of integration become readily apparent to the authorities, but they have begun pushing for political representation.
Different sections of society vie for control, initially politically, due to fundamental disagreements over not only what traditions or customs should be acknowledged, but also what legal and moral system should be followed, how society should order itself etc. Compounding this is the fact that almost invariably minorities have a stronger allegiance to their ethnic homeland than the land they currently reside in.
