Leftists never let reality get in the way of their favorite slogans, e.g. "Diversity is Strength." There's a reason why countries like Switzerland, the Scandinavian nations, and Japan are known for civility and prosperity (or at least were known for this until some of them stupidly opened their doors to the Third World), while multicultural societies breed crime, ignorance, and squalor.
I think it’s pretty ironic that you use Switzerland of all places as an example of ethnic homogeneity.