People want inflammatory content like a moth wants a flame. Facebook amplifying a signal from the lunatic fringe preys upon the need of non-lunatics (or different-thinking lunatics) to argue against ideas they consider dangerous or just wrong. As a side-effect, it makes the ideas appear more mainstream, which has the effect of making the ideas more popular. This further increases the compulsion of non-lunatics to address the ideas.
I'm not sure if that qualifies as being what people 'want' or not, but it seems like it's profitable.
I'm not sure if that qualifies as being what people 'want' or not, but it seems like it's profitable.