Are we really doing that when we ask people for comments? Are we really doing that when we freely distribute the source code? When we encourage individuals to look through the source code and contribute patches that change the software to better suit their needs?
A more inherent problem with this line of reasoning, though, is in the basic argument. Even though we are acting like egoists, we are actually displaying beneficent motives. The argument states that it's in everyone's best interest if we just but out.