I really don't see any exploitation. Being intentionally tautological now, builders build, workers work and actors act. Now, I can't see a black actor playing an white guy, so I can only assume he's supposed to play a black guy (duuuuh). Can't really see the upset other than the obvious poor quality of the movies, though I can safely assume we're not dealing with a bunch of black Robert De Niro's.
How can you possibly exploit someone by giving a job that perfectly fits their background and training? Are the employers to be despised just for eventually making a profit out of these shit movies? Maybe, but it doesn't have anything to do with the colour of the actors imo.

Paint shop proo posters

there's some movie i'd watch. For the storyline of course ;)

I have lusted over Pam Grier many times

I posted, on this site, some different Blaxploitation stuff on my birthday last year
Blaxploitation (20 pics)
https://izismile.com/2010/10/18/blaxploitation_20_pics.html