I agree with the premise of the thread, but not necessarily the reasoning behind it...
I would argue that the predominant factor is religion... religious people are dumb... religious people also tend to vote republican (simply because republicans cater to their demands/ideals)... herego, republicans are dumb by proxy, but not for the assumed reason in the OP
Though, I suppose you could argue that it's not, "religious people are dumb", but rather "dumb people are religious"...
Is this the new, "Which came first, the chicken or the egg?"
I also read about religion and intelligence and would agree with your findings that low iq people usually are very religious.
And very religious people usually tend to discriminate against other religions and certain religious groups.
( i.e. there is only one true religion )
One such group that sets a great example would probaly be the KKK.
Don't forget, religious people also argued in favor of slavery (racism)
James Thornwell, a minister, wrote in 1860, "The parties in this conflict are not merely Abolitionists and slaveholders, they are Atheists, Socialists, Communists, Red Republicans, Jacobins on the one side and the friends of order and regulated freedom on the other."
(by regulated freedom, he means the freedom to own slaves as your property... not freedom for black people)
(in much the same way that today, "religious freedom/liberty" means freedom to discriminate against homosexuals)
http://religion.blogs.cnn.com/2011/04/12/how-the-bible-was-used-to-justify-slavery/They used the exact same passages from the bible as they use to condone their homophobia (with the addition of the part about Noah's son, Ham... god curses his decendants to be "servants", which religious people decided means black slaves... Ham = black = slaves)
Slavery is condoned in the bible in at least a dozen different places... and condemned zero times
The bible is all about tribalism... and hating anyone who doesn't look and believe like you do... it's full of genocide... the Israelites murdered countless civilizations... literal genocide, several times in the old testament