Elliot Smith is a big big fave of mine. In high school I missed out on a chance to see him live because I didn't know who he was. By the time I did he was already dead.
If you can get bootlegs of his live covers as well as his albums. Here's him covering the Zombies.
Isn't he ever? Elliott Smith and The Red House Painters are my go to terrible mood artists, and the fact they occupy different poles of the depressive spectrum is interesting.
Oh me too. I'm particularly fond of prog metal and hardcore/post hardcore at the moment. Heaven Shall Burn is a badass German Metal/Hardcore band of mostly vegan leftists.
Some days just feel they are made for sad boy music.
The song I linked wasn't specifically ideological, it's just a cool cover of an Edge of Sanity track. Apparently their fans are well known for beating up nazis in the German metal scene, but that's third hand information.
Classic hardcore punk is great; at least 30% of the lyrics are about hard left politics. I'm fond of Defiance , though they aren't quite as crusty.