A quality may be both a virtue or a vice, depending upon how it is applied. Diversity of skills, for instance, is essential for a nation. But diversity of purpose weakens a nation.
Take Japan. Japan has a diversity of skills and unity of purpose, buttressed by racial homogeneity. America, sadly, has less and less of any kinds of skills, & suffers from a metaphysical & moral vertigo that has all but annihilated the possibility of unity of purpose. But the American left sees diversity as yet another tool of social revolution and "change"–– yet another pretext for the enforcement of political correctness--a political correctness ironically meant to eliminate all diversity so that all that remains are the ideas & opinions of the left.