There are two very angry songs that came to my mind the very moment I read the thread title.

"Shortenin' bread" - this dramatic story about "mama's li'l chillen" dying with hunger and mamma being jailed because she made bread from her master's corn in my opinion is a little masterpiece of folk lyrics.

"Pie in the sky" - a slap into the face of church and salvation army.

Kinda revolution spirited, these two. But that might be the right spirit talking about rich and poor on christmas. Think about it.