I, on the other hand, don't tend to walk around with glowing atheist belt buckles. I've been atheist since I became aware of the term, but my material is not all about religion – not by a long shot – and when I do address the topic it is to point out where religiosity meets discrimination. Many comics write about what makes them angry, or, at least, what they observe in the world that is at odds with how they feel it ought to be. This is the case when Seinfeld talks about muffins or McIntyre talks about Argos (brilliantly, I hasten to add). I just happen to be less preoccupied by parking spots and soup nazis, and more by homophobes and creationists.
Most people don't know I'm atheist, though I do confess to a fair collection of kitschy t-shirts advertising the fact in one way or another (though I tend to save those for times when I don't plan to meet up with anyone I know). But here on the Internet, where I have yet to meet one more godless than myself, I like to part company with my more conciliatory brethren, who are happy with benign mistakes as long as they lead to beneficial results, and take it a little further: it's easy to condemn religion for its ill effects; it's a little more sporting to me to criticize it for being rooted in irrational soil to begin with. I'm glad that some people manage to be religious while embodying it in a way of life that coexists easily with mine, but I'd be happier if they took a more direct route to that understanding.
Granted, pure rationality is neither attainable nor desirable. And I honestly don't have any desire to convert as many people as possible to my way of thinking. But I think as a general rule that you should still endeavor to see as clearly as possible, even at the cost of personal discomfort, and I like the idea of serving as a prod, a stimulus, an irritant, a gadfly to perhaps push other people in that direction.
By the way, it's funny, that Browning quotation -- when I heard it, I took it as a suggestion that heaven is actually unattainable, simply a projection. I don't know what he meant by it, though.