Nope, anger really is the problem. People's anger comes from a lot of places; distribution of wealth is just one option (particularly favored by intellectuals). Other people (generally not intellectuals), are angry at immigrants, at women who have abortions (and the lawyers who let them), at blacks, Jews, homosexuals, communists, Colin Kapearnick, etc.

If we were to accept your argument that "anger isn't the problem, but the cause of the anger is the problem", then we would have to accept these angry people's solutions: immigrants should be returned to their homes (or killed), women who have abortions should be prosecuted for murder (or killed), blacks/Jews/queer folk/etc should be killed, and as for Conlin, well, that last solution solves that one, I guess.

Another problem with the "argument for anger" is the tacit assumption that problems can't be identified or changed without anger. I have found the opposite to be true. Anger can be a handy divining rod for injustice in the world, but it is an equally good divining rod for personal ignorance. In short, anger lies. Moreover, it makes solving big problems very difficult, since anger fogs the rational mind.

Ironically, it is impossible to know where the anger is leading you, to change yourself, or to change the world, until you give it up.