i have been places where store owners/operators have mistreated a black person (employee or customer) while i was standing nearby. Later that day i posted signs all around that say "STOP - Racist owned/operated establishment. Do not let our people be downpressed any longer - support the black community". This has been effective in that a very popular car wash had NO customers until the man came to get the money out & tore down all the signs i had posted. Of course, i continued (i conveniently lived across the street)and eventually, he sold the business.