Perhaps I should give people more credit and assume that they believe that an atheist is very likely to be a liberal, but doing even a little bit of homework will get beyond the stereotype.We would be so fortunate if only the stereotype was an inaccurate one! Inductivist may not be off the mark in describing atheists in the Steveosphere's orbit, like the scientifically-minded prodigies at GNXP. Among the general public, however, presuming most atheists to be leftists is not unreasonable, even if it's not quite precise.
The GSS shows that among atheists (N=252), 47.6% self-describe as being somewhere on the liberal end of the political spectrum. A further 29.0% are moderates, with the remaining 23.3% on the conservative side of things. So it is more sensible for one to assume, absent any other information, that there is basically a 50/50 chance that an atheist will also be a leftist.
Among the public, 26.8% self-describe as belonging on the liberal side, 38.7% say they are moderates, and 34.5% count themselves as conservatives of some stripe. Thus the odds of finding a leftist at random among atheists are nearly twice as great as they are of finding a leftist at random among the general population.
The graph on the left looks at atheists alone. The graph on the right represents the general population. Green-on-down represents those on the liberal side of the political spectrum, yellow those who consider themselves moderates, and orange-on-up those who are conservatives of some degree. (Click on either graph for greater resolution).
The stereotype of the liberal atheist becomes untenable when it is conversely assumed that because there is a good chance atheists are leftists, there is similarly a good chance that liberals are atheists. In the US, theism continues to be the dominant position across the political spectrum. Fewer than 3% of those on the liberal side of the political spectrum describe themselves as atheists. Eight percent are agnostic, while an overwhelming 89% are theistic.
As the graph below shows, the more liberal a person describes himself as, the less firm his theism becomes. But among the general population, atheism and agnosticism are rare even among those on the left. Magenta represents those who are certain God exists, red represents those who are certain God does not exist, and the colors in between represent varying degrees of confidence in the existence of God.
GSS variables used: GOD, POLVIEWS