I made a conceptual jump that I'm not sure this post (or its author) intended, but that left me with a better impression of it than most people seem to be expressing.

I agree that things actions like writing a letter to the editor may have a low rate of return in bringing new persons to the cause, but I believe that they serve very well at making people who are already pro-rational in name more likely to take greater actions at a later date. E.g., I didn't get involved in running the skeptic group at my university until well after I publicly supported skepticism and atheism in letters to the editor of my campus newspaper. That is, I think maybe the point of this post is encouraging the sort of person who is now just reading LessWrong because it is shiny to go out and start doing things instead. The world changing will come later.

See chapter 3, "Commitment and Consistency" from Influence by Robert B. Cialdini or this post on the same by Anna Salamon and Steve Rayhawk.