Caduceus Mercurius a dit:
I often listen to sad or angry songs, but not sad or angry bands making sad or angry albums.
I guess it depends on the role you want music to have in your life, and how you want it to engage you (and only you can gauge how the music you listen to affects you)
Being sad or angry, whether it be caused by social injustice or perceived hypocrisy and flaws inherent in society, or personal weaknesses and failings, are all equally real and valid parts of the human experience, and need to be expressed and understood. Otherwise expressions of these conditions simply wouldn't exist, and nobody could relate/would want to listen to them.
A great deal of 19th century music and literature is profoundly unhappy with just cause--reacting to the constrictive pressures and double standards present in a frequently misogynist and claustrophobic society. That century's music was an outright rebellion against the stifled music of the classical period, was rich with experimentation and expression, and sadly its artists frequently lived very short and miserable lives. Fast forward a century, a huge part of late 60s to 80s underground music was reacting to the social injustices of the time, be it nonstop war, George Bush I, homophobia, hypocrisy rampant in middle-class morality, etc etc etc each expressing their experiences in their own way and leading to new avenues of expression.. from that era sprang completely new genres like punk, industrial for example.
Art is about transference of subjectivity, which exercises empathy. As our society continues hopefully to improve itself, it's blights and dark sides will be pointed out by its artists, who are usually the ones suffering and driven to express it in order to deal with the darkness and understand it. When society has embraced, confronted and solved all of its ills, then all literature, music, and painting will be happy.