What we believe matters. It matters because our behavior is often predicated on what we believe to be true. The way we treat people, how we spend our time and resources, what power structures we support, which social mores we reinforce, and so on, are all informed by how well we understand reality. Assumptions about gods, divine morality, sacredness, and the nature of the human condition within the larger scope of the universe makes a big difference in all those choices we make. Hence, any idea that religious beliefs are entirely private and beyond the scope of public concern, inquiry, or criticism is both unfounded and dangerous.
Criticism of religious beliefs is not in any way inimical to religious liberty. The freedom of conscience and the right to belief and worship is in no way undermined by open inquiry, disagreement, or even mockery. To test this, ask yourself if the freedom to vote and act politically is undermined by open inquiry, disagreement, or even mockery...obviously it isn't; we proudly do all three here at DKos without worrying if we are treading on the rights of our fellow GOP citizens. However, there is a common sense that religious beliefs occupy a special place, a place free from inquiry, criticism, and mockery. This sense is an expression of religious privilege and it has done much harm to the project of human decency and progress.
Believe it or not, being an open atheist is a serious social detriment in most places in America. It can have a profound negative impact on employment, friends, and even family. As has been noted, being an atheist pretty much guarantees one will never be elected to public office. Even a DKos front-pager feels free to call us less than human. What this means is that there is often significant social pressure to either believe, pretend that one believes, or at least be silent about one's lack of belief. This must change if we want to forward a more open, free, and just society.
Much of the atheist movement in the last decade has been about tearing down religious privilege. It demands the right to say "I don't believe! And neither should you!" You don't have to like it, and you might even be offended by it, but them's the breaks living in a society founded on the idea of the free expression of ideas. Please note, not one single prominent atheist has lobbied for anti-religion laws (outside of those that protect the helpless)...no one of consequence promotes outlawing religious practice or belief. But we do demand the right to say that religious beliefs are wrong, silly, or harmful without the threat of economic or social harm.
What people believe matters. The right to discuss, disagree with, and even mock those beliefs also matters. Religious privilege is a cultural toxin that must be washed away, and that process is not always going to be pretty or polite. It will often be contentious and even offensive for the obvious reason that it calls into question fundamental and deeply held beliefs, both about the world and ourselves as humans. Naturally, some voices will be more eloquent and thoughtful than others, which can certainly be said of theists as well. This is the way of things when humans disagree. But the movement has started to snowball. Non-believers will no longer be quiet. It is my hope that the larger progressive movement will eventually embrace us and openly support our right to speak and enjoy all the privileges of our theistic brothers and sisters.