Bringing a windows guy into a unix shop, or hiring a sales guy too early at a product development stage startup, or hiring a stupid or lazy person would be real diversity of a bad kind. Good diversity is bringing in people with domain expertise outside your core specialty, like having a font and calligraphy aficionado on your os team.
Superficial diversity is really overvalued.
Superficial diversity is really overvalued.
And very undervalued by people in the majority ...
I really haven't observed ethnicity or race as a primary factor in team dynamics. Even first language, assuming people have a minimal level of fluency, hasn't been a major factor; even with my minimal French, I've ended up hanging out with French video gamers and sci fi fans (all 3 of them at a big base; they spoke maybe 100 words of English) vs. a bunch of other Americans.
Volitional things like the kind of music you like, the job you do, your hobbies, etc. are really a much bigger factor, at least in my limited experience, than race or ethnicity.
My current company had no diversity until I joined (the founder and employee #1 even went to the same school), but it never struck me as being worth thinking about. I'm honestly curious, what benefits do you get from a company with ethnic diversity?