The cartoon is both accurate and I suspect aimed more at those who irrationally hate atheists than at atheists themselves.
Certainly accurate. This is a link to a rather interesting recent Newsweek article in which this nugget showed up
http://www.msnbc.msn.com/id/14638243/site/newsweek/"In a recent NEWSWEEK Poll, Americans said they believed in God by a margin of 92 to 6—only 2 percent answered "don't know"—and only 37 percent said they'd be willing to vote for an atheist for president. (That's down from 49 percent in a 1999 Gallup poll—which also found that more Americans would vote for a homosexual than an atheist.)"
We atheists certainly DO meet up for that purpose, or at least some of us do. I wish more did, because then we may be able to get political clout more in keeping with our real numbers. Atheists easily outnumber Jews and Muslims in the US, but we do not have the media call us every time some religiously-inspired lunacy is afoot. Jewish and Muslim anti-defamation spokespeople are on the rolodex of every reporter in the country. We only get printed if we buy ad space. Before I moved I belonged to the second largest locally based atheist group in the country - Minnesota Atheists. We had about 300-400 members but not all active. We managed to keep a cable show going (if you ever saw a public access cable show called Atheist Talk with a fat strangely-accented interviewer that's me :-) !) for a few years. We managed to keep up a Winter Solstice dinner that raised money for charity and various special interest groups including a Toastmasters club for nonbelievers! Even then though, we never could get enough money together for a real building, and could never get much media or political clout. Some lobbying efforts were made, but nothing like those of other minority viewpoints on religion which were much smaller in number but better funded.
If atheists could be encouraged to be joiners we might one day be able to gain the kind of influence and success that Jews and gays and other often-reviled minorities have. Sadly the nature of the beast is otherwise. Like someone said, it's a bit strange to have a club for non-golfers, although I should point out that non-golfers are not marginalized and despised like atheists, and golf does not control a large part of political motivation for the majority like religion does.