Gah, "politically incorrect" can go jump. It might not be nice or good that, for example, Aboriginal Australians make up 2% of the population in general but make up 30% of the jailed population, but pretending that there isn't a problem because it would be "politically incorrect" to mention it isn't going to solve anything! (This is one of my pet aggravations - when I was studying, I told my grandmother that I wanted to study Historic, not Aboriginal, archaeology. "Isn't that a bit politically incorrect?" she asked. No, it's what I want to do with the rest of my life!! People use that term for the absurdest things.)
Anyway, dragging this post back on topic . . . I'm not at all surprised that they have evidence to back up their conclusion. It makes sense. Unpleasant sense, major-problem-needing-to-be-fixed sense, but still sense.