I've always gotten the impression that PG's essay are aimed more at people who are somewhat unsure of what to think on a subject, who aren't fully informed and haven't reached any strong conclusion yet, and PG seeks to present his thinking and conclusions in an edifying manner that assumes that the reader can recognize and appreciate good reasoning. Writing for this audience (as opposed to targeting people who cling to conflicting beliefs) is not preaching to the choir, and is probably much more productive than railing against people who "just don't get it".
Making a compelling argument to a receptive audience. Versus: attempting to convert an unreceptive audience. Or: merely saying something that everyone in the audience already believes (which would be preaching to the choir).
Given the volume of discussion that often comes about due to pg's essays and the fact that it is rarely entirely agreement I think those essays hold a good deal of value even if they are not aimed at a universal audience.
