Some people are conditioned to yearn to be outrage about something. Spend an afternoon and watch the daytime tv shows...its terrifying to watch how the audience reacts to things. There is a whole universe of extraordinarily dumbed down people in our society.
And Facebook/Twitter are the perfect medium for them. Not only can they satisfy their desire to be outraged, but they can take action - in the form of posting a comment. This may get them the other thing they desire - attention.
The Oprah generations spreads their wings.