I'm just now starting to read this topic thread, thus I haven't yet read the Pew report, but what I notice thus far is that the articles that are discussing it are only comparing conservatives and liberals who are WHITE. For example in the articles there appears to be no mention about black liberals versus whites (liberal or conservative). Maybe the black liberals have less mental problems than white conservatives. ;)
Studies that I have seen say that atheists in the USA know more facts about the Bible (such as the names of the biblical books and the commandments of the 10 commandments) than do Christians in the USA; that a higher percentage of atheists in the USA have higher formal education and higher pay than do Christians in the USA (with Christians of very conservative denominations/churches [such as baptists, Mormons and JWs] having less education and pay than those of liberal denominations/churches [such as Unitarian/Universalists and Episcopalians]); that the percentage of atheists in the USA who are political liberal and aligned with the Democratic party is higher than people in the USA who are not atheists.