EU and China are perfect inversions of your point.
China suppressing ethnic, cultural, and linguistic diversity for homogeneity has caused immeasurable suffering and imperialistic destruction.
EU explicitly embracing ethnic, cultural, and linguistic diversity for heterogeneity has brought more peace and prosperity than ever before to a continent in perpetual conflict for nearly all of human history.
China suppressing ethnic, cultural, and linguistic diversity for homogeneity has caused immeasurable suffering and imperialistic destruction.
EU explicitly embracing ethnic, cultural, and linguistic diversity for heterogeneity has brought more peace and prosperity than ever before to a continent in perpetual conflict for nearly all of human history.