Maybe you could argue that multiculturalism does have some philosophical use in terms of promoting some absolute truths, since the value of peace that comes from harmony between different cultures is greater than the conflict that would be caused by allowing inferior cultures to be assimilated.

For example, when people feel their way of life is under threat, they often take it to an extreme to protect their identity. And this polarisation is what gives us Wahhabis and Jihadists etc.

Just a thought, couldn't leave without arguing with you PVC.