I don't think you should limit it to folk singers or songs about war/peace. For example, Macklemore, the same guy who brought you Thrift Shop, also has a song called Same Love in support of Gay marriage and equality. Meanwhile you have Ry Cooder putting out that song, No Banker Left Behind, which I'm sure you can guess what that's about. You also have Lupe Fiasco, who is constantly putting out what is essentially protest music. This song embodies what he's about particularly well, which is racial equality and Occupy Wall Street (back when that was huge). So there is a lot of music out there, however, it is not as concentrated or confined to one or two scenes as it was in the past. You don't have artists making exclusively music for protesting or with the purpose to incite rallies, but releasing it along with their other music.