It is you who has a poor misunderstanding of his intent. Dave Silverman is the president of American Atheists. He's not out to convince the religious that they're wrong; the mere fact there are so many incompatible religions should answer that question for you.
American Atheist's main goal is religious equality (it is unconstitutional for our government to make Christmas a national holiday without making every other religious holiday a national holiday -- they should change the name for the 25th off), and showing atheists that it's "okay" to come out.
Despite what Hannity says, if you think that there aren't at least hundreds of thousands of people in America (or more) who don't really believe, but go to church/act like they do for family/social reasons, you are highly mistaken. There are even many priests and pastors who have made a career out of religion, who have lost their faith and are wracked with what would happen if they were honest about their changed beliefs.
The Clergy Project - Home Page