First, liberals love to use the mantra "Celebrate Diversity", but this phrase is contradictory with classical liberalism. Liberalism tells us that race and color do not matter. How can "celebrate diversity" and "color doesn't matter" both be true? The later suggests we should be a color blind society. The former advocates a color based society.
Second, liberals love to say "Diversity is our great strength." No it isn't. Liberty is our great strength. Liberty made us great, and in turn created diversity as millions came from foreign countries to taste it. Diversity did not create greatness. Greatness creates diversity.
Third, liberals do not even believe in diversity. This is best expressed by the economist Thomas Sowell who said "The next time some academics tell you how important diversity is, ask how many Republicans there are in their sociology department".