Hey everyone, so I've been thinking about this question now because it's a good one, and I feel my answer was very poor, so I've erased the whole thing and made a new one:
We become moralists when we are convinced that we have supreme knowledge and other people must understand this knowledge for the world to become a better place (think evangelists). As anarchists, our goal is to dispel this notion, but since anarchism is an ideological position, then often we become like the evangelists themselves. The truth is that anarchists do not have superior knowledge and are not "better people" than the rest of society. You can't make the world a better place by making people "get it".
Anarchism is useful in the sense that it criticizes the roots of our culture. However, anarchists are also strongly influenced by the things the try to criticize (capitalism, the state, morality, ect.) In "Hello, a greeting from nowhere", it points out how Christianity has deeply influenced our thinking in the United States, and Christianity is a heavily moralistic ideology, so not being a moralist is very difficult. In order to avoid being moralists, I feel that we must dispel the idea that we are superior because of our points of view.