"a few of them see it as an opportunity to express contempt for racial minorities.."
I frankly just don't believe this. We've been to no end of Morris festivals over the years, in many places, and must have watched dozens and dozens of different blacked-up sides, both Border and Molly. My husband always tries to get photos of himself, posed with groups of various types of Morris, for his collection. No-one has ever edged away, been frosty, looked askance or uttered anything racist or discouraging.
On the contrary, they have hugged him, laughed with him, plonked their hats on his head for the photos, and invited him to dance so I can take some pictures. Many now recognise him from previous visits (he always wears his Ivorian costume)
I feel most indignant on their behalf that anyone could suggest there is racism among blacked-up sides. Morris folk are the most friendly, open and charming people you could ever meet.