The quote you complain about obviously can't be about racial diversity. He introduces a problem with diversity, and then links it to problems which, he says, an

The quote you complain about obviously can't be about racial diversity. He introduces a problem with diversity, and then links it to problems which, he says, and emphasizes in TFA, have increased very sharply since 2010-14. But racial diversity has been rising steadily for decades with no inflection point near 2014. Furthermore, he goes on to explain how social media leads to a fracturing of cliques and a tendency to maintain parallel lives. It's clear from this context that the "diversity" he's talking about must be a sort of diversity of perspectives and not of heredity or anything else like that.