A 15-year study of young people in Finland found that education level, nonrational thinking, cognitive potential, and cognitive performance were not associated with social intolerance -- i.e., intolerance toward different attitudes, lifestyles, cultures, or values of others. On the other hand, higher social intolerance was associated with low flexibility, high perseverance and low persistence. The study was published in Brain and Behavior. ...
Just spitballing but this could have something to do with the fact that higher education is expensive (even if only in the sense of lost potential earnings) so that tends to filter out minorities. Then those grads go on to jobs which require said degrees, which means their coworkers tend to be from similar backgrounds.