[soundnote]

Presumably: The bad sort is a diversity where people look different but all think more or less the same, so the proponents can pat themselves on the back for being good and openminded people but don't actually have to deal with genuinely different people. You can see it in how those sorts tend to despise people who look the same as themselves but have different views and how their love of diversity disappears the second the different-looking person doesn't hew to their ideology.