Isaac Hayes's role during the Civil Rights Movement hasn't been as touched upon as his musical and cultural impact. Hayes had acknowledged that "Soul Man" was directly inspired by the racial violence of 1967, but there weren't many interviews I could find about his activism. The best summary of Isaac Hayes' influence during the Civil Rights Movement came from a fascinating graduate thesis paper from 2015. Jason Danielson of Iowa State University looked at the effect of the music label Stax Records on the Civil Rights Movement in Memphis, Tennessee. Isaac Hayes was an in-house songwriter, session musician, and record producer for Stax.

The following is an excerpt from Danielson's thesis. I recommend everyone interested in musical culture and the Civil Rights Movement read.

The Role of Soul: Stax Records and the Civil Rights Movement in Memphis, Tennessee —

"In addition to his enormous career at Stax, both as a writer and producer in the 1960s and as an performer in the 1970s, Isaac Hayes performed more charity work and local and national community activism than most of the Stax team. He sought to provide low-cost housing for the poor and elderly, helped quell violence and negotiate curfews with city leadership during black uprisings, performed at Wattstax to raise money for local and national organizations related to the Watts uprisings, and was honored by numerous organizations including city governments, civil rights groups, and the Academy Awards (for Shaft).

Hayes’s philanthropic and activist work, like his music, defied artificial categories; while he clearly desired black economic development and wrote music for a film about a tough black police officer, he also engaged in cooperative work with white city officials to avoid race riots, and even joined in the campaign for black Democratic congressional candidate Harold Ford in 1974."