Since my series of posts on changes the relationship between political views and happiness trailed off into "something happened, but it's hard to say what it was," I wanted to do something that came to a definite conclusion. Arthur Brooks said "people at the extremes are happier than political moderates." He speculated that this was because "extremists have the whole world figured out, and sorted into good guys and bad guys. They have the security of knowing what’s wrong, and whom to fight." As you can see in this post, no such pattern is present in the GSS: average happiness increases as you go from left to right, except recently it's fallen off among people who say they are "extremely conservative." What if you look at happiness by party identification?
So it doesn't seem to be the case that extremists are happier than moderates. Rather, as I said a few posts ago, the pattern seems to be that people who are interested in politics are happier than people who aren't. Further evidence can be seen in the relationship with political views, people who answered "don't know" to the question on political ideology are the least happy group.
Brooks didn't give a link to his source, or any information about it, but if I were a betting man, I'd bet he did one of two things: (1) mixed up the patterns for party identification and ideology or (2) used a survey that counted "don't knows" on a liberal/conservative rating as moderates, which is sometimes done.