When you read headlines about the rise of the so-called "nones," or people who don't consider themselves part of a religion, that's what they're mostly referring to: the shruggers. They might be intensely spiritual or perfectly apathetic about faith, but for some reason or another, they don't self-identify as definitively atheistic.

Among those who do identify as atheists, though, the tone taken toward organized religion, especially recently, has been more shout-y than shrug-y. At the 2012 Reason Rally in Washington, D.C., for example, "a band fired up the crowd with a rousing song that lampooned the belief in 'Jesus coming again,' mixing it with sexual innuendo," Cimino and Smith write. Attendees sported T-Shirts and signs with slogans like "I prefer facts" and "religion is like a penis" (involving a rather extended metaphor). There was a life-sized Jesus puppet.

This wasn't just some small enclave meeting for some drinks and Judeo-Christian trash talk; there were between 8,000 and 20,000 people there (a puzzlingly wide range of estimates, but still: in the thousands). Richard Dawkins, one of the keynote speakers, encouraged attendees to "ridicule" people's faith. Not all atheists take this tone toward faith, but it's a somewhat common posture, especially among some of atheism's most vocal advocates, including Dawkins and people like PZ Myers and Bill Maher.

"It's definitely one of their strategies," said Cimino. "There is this strong attempt to be kind of irreverent." This is a quality particular to "new atheism," he said, a term for Dawkins-style arguments against faith, which rely heavily on science and invocations of rationalism. "There's a sense that once you make fun of it, you can kind of demystify religion," he added.

But there's also a sense, at least in reading Atheist Awakening, that derision toward faith among outspoken atheists is partially a product of accumulated bitterness. "It is hard not to come to the conclusion that atheists have spent a far greater deal of time thinking and writing about religion than religious people ever have of atheists as a group," the authors write. American voters disapprove of atheist politicians; parents dread the possibility of atheist boyfriends and girlfriends for their kids; and in general, the public feels less warmly toward non-believers than almost any other faith. Being an atheist means defining oneself in opposition to theism, but that doesn't necessarily go both ways. America is a land of ambient distrust of people who don't believe in God, but mostly in the way of a high school full of queen-bee cool kids and nearly invisible geeks.

This milieu shaped the rise of what you might call aggressive atheism, the kind that mocks and dismisses religious belief. As Cimino and Smith point out, this outspokenness has helped atheism gain visibility and coherency as a movement. But it also has downsides.