What were some social issues that were written into song lyrics as a form of protest?

Great Question

Many songs have been written to address social issues of a given time.

Michael Jackson's famous song 'Black or White' was written to address racial divides and promote harmony.

Another of his songs 'They Don't care about us' was addressing a similar issue of social injustice and discrimination.

Bob Marley was famous for writing songs in memory of a 'motherland' Africa