Harvard political scientist Rober D. Putnam, after undertaking a massive study, determined diversity kills citizenship.

What are the effects? (especially when forced by law)

Lower confidence in local government, local leaders and the local news media.

Lower political efficacy – that is, confidence in one's own influence.

Lower frequency of registering to vote, but more interest and knowledge about politics and more participation in protest marches and social reform groups.

Higher political advocacy, but lower expectations that it will bring about a desirable result.

Less expectation that others will cooperate to solve dilemmas of collective action (e.g., voluntary conservation to ease a water or energy shortage).

Less likelihood of working on a community project.

Less likelihood of giving to charity or volunteering.

Fewer close friends and confidants.

Less happiness and lower perceived quality of life.

More time spent watching television and more agreement that "television is my most important form of entertainment".

Notice how Japan, China and Saudi Arabia don't have diversity forced on them and still function just fine.