The reason religion and stupidity seem to us to be related is because (I personally believe) of the correlation between lower intelligence and the susceptibility to influential movements/schemes. Those same people who have been coerced into believing a certain religion might just have easily been coerced into adopting atheisim if atheism was the primary belief system of America and its influence was felt everywhere.
I also think it's interesting that one of the researchers involved in the study admitted that some proclamations of belief in atheisim and liberalism might stem from a desire to exhibit elitism and intelligence. If that's the case, it's practically the same as "unintelligent" people adhering to religious beliefs.
Still an interesting article, but I have to question the correlation between religious tendencies with lower IQs. I think lower intelligence makes people more susceptible to any primary influence of society.
Anyway, here's an article by Leonard Pitts. I don't typically enjoy all the material he writes, but this is a good one:
http://www.miamiherald.com/2010/02/13/1478213/dear-sarah-say-it-is-so-run-for.html