Marvin Gaye released his police brutality inspired (sounds familiar even in 2017 sadly) What's going on in 1971. He produced it himself and it was his first step away from the Motown sound and ended up as #2 in Billboard Top-100 and sold over two million copies becoming one of the fastest selling Motown single ever and scored two Grammy nominations for it.
Gordy was against it when Gaye told him he had a protest single coming up he wasn't pleased, and after hearing it refused to release it as a single. Gaye in turn went on strike and refused to record anything. Eventually Gordy gave in and the rest is history.
Cyndi Lauper's 1987 cover version is maybe the best known. She reached #12 in the US.
In 1988 the song was used by Live Aid Armenia to help the earthquake victims,
and in 2001 by Artists against AIDS (#27, UK #6)