Diversity is strength...for Capital. But diversity is weakness for Labor.
The more diverse a nation, state, city, neighborhood, workplace etc, the less united is Labor. Diversity engenders factions. Factions weaken unity. A less unified Labor is easily preyed upon by Capital.
What sort of diversity creates factions?
1. Size: the larger the nation, state, city, workplace etc, the more factions.
2. Distance.
3. Race.
4. Culture.
5. Nationality
6. Language.
The fact that factions and diversity weaken the position of the majority has been well known to Capital for centuries. In fact the so-called 'founding fathers' (aka Capital) deliberately discarded the Articles of Confederation and replaced them with the Constitution because the structure of the government created by the constitution would cause factions in the electorate, weakening the position of Labor and strengthening the position of Capital. See, e.g., the federalist papers that were written by the Father of the Constitution, Madison (worth 100 mill after he got his inheritance) and see also his notes on the constitutional convention.
I have given you the theory. Let us examine the evidence: for western nations, let us compare two extremes: one, very large and diverse, the other, small and relatively homogeneous.
The USA versus...denmark, sweden, iceland, austria et al.
Where is it that the people enjoy more time off? Where is it that the people have more control of their governments?
Now, recently denmark, sweden, austria, et al are "enjoying" more diversity via mass immigration.
How is that increased diversity impacting the quality of the lifestyle enjoyed by the citizens therein?
You know the answer.
Now you have the theory and the data.
But you will not understand what I am saying because this is not what you have been taught since youth. Hmm...another of the puzzles of mankind upon which to ruminate....