Wearing denim was a function of being poor not of style, and those like James Brown that made it out wanted as far away from it as possible. This logic also played into the strategies of organizers like Martin Luther King Jr., knowing that any and all imagery of people involved in the movement would be criticized harshly for whatever they said, did, or wore. Those involved in sit-ins, boycotts, or other protests of racial injustice often wore their “Sunday Best”, as doing so would play better on the evening news.

https://www.heddels.com/2020/01/martin-luther-king-jr-and-the-radical-styles-of-civil-rights-activism/