Diversity is inherently destructive. It make dealing with a population very difficult. One needs to unite the population under a common ideology. The ideology doesn't matter as much a the unity under it. Religion, patriotism, something. United we stand, divided we fall.
I don't think liberalism is the problem. Liberalism is freedom, freetrade, equality under the law. these are not bad things. Multiculturalism can even be dealt with if people can be otherwise united under a common ideology. All of these different ideologies with no common ground, that's the problem.