I have personally never been a fan of "multiculturalism" as a social decision-making guideline, as I feel it is one of social ideas out there which is completely bad, with no good aspects to it at all.
I prefer the social idea sometimes referred to as "the melting pot” or as I like to call it: Assimilation.
At least if the goal of your social decisions is to bring a community into a closer and more intertwined relationship with each other.
Multiculturalism, in my mind, can accomplish this on a small scale, by supporting or promoting an "us against them" mentality.
Assimilation, on the other hand, (at least in my opinion) is a far better option.
While it may blur the lines and even cause the loss of some aspects of the former culture and society which a person entering it used to have...That is the goal, at least if you are attempting to produce a society along the lines of that I described above.
In my mind, only if the entire world is assimilated into one single culture (or at least the majority of it) will actual world peace/harmony/whatever result.