The notion that cultural diversity necessarily makes us stronger or better is simply not true. In general the more homogeneous a society the better things tend to work.
Like socialism, cultural diversity is a talking point of the progressive left.
If you want proof, take a look at what this failed concept has done to Western Europe.
By contrast, Japan and Eastern Europe have taken the best of western culture and discarded the liberal baggage to produce more stable, citizen friendly societies.
They have also shown the value of physical barriers to stop the mass movement of uninvited people. Japan is protected by an ocean and Eastern Europe by border fencing.
— Gregory H. Bontrager, Hutchinson