What is a Social Justice Song? - Dylan's Hard Rain?

Justly complaining? Proposing? Moving others to action? Raging? What makes something a social justice song? As I move (ever so slowly) to pulling together the songs I've posted here and the tracks that others have nominated, the question becomes more important. One day, we'll vote. First, any additional songs suggestions or arguments for what makes an excellent social justice song are very much appreciated!