A lot of people believe that the smears about President Obama being a radical Muslim are rooted in badly veiled racism. I would argue, though, that it's rooted in something equally insidious. To my mind, this is an attempt to introduce a religious test for office, and in so doing effectively lobotomize both Article Six of the Constitution--which forbids religious tests for office--as well as the First Amendment.
If you'll remember, back in 2006 Roy Moore raised a stink about Keith Ellison becoming the first Muslim to serve in Congress. Moore argued that Ellison should be denied his seat because a Muslim could not honestly take the oath of office. Consider the last paragraph of Moore's screed:
Enough evidence exists for Congress to question Ellison's qualifications to be a member of Congress as well as his commitment to the Constitution in view of his apparent determination to embrace the Quran and an Islamic philosophy directly contrary to the principles of the Constitution. But common sense alone dictates that in the midst of a war with Islamic terrorists we should not place someone in a position of great power who shares their doctrine. In 1943, we would never have allowed a member of Congress to take their oath on "Mein Kampf," or someone in the 1950s to swear allegiance to the "Communist Manifesto." Congress has the authority and should act to prohibit Ellison from taking the congressional oath today!
Based on the smears against Obama, all you need to do is change a few words and that paragraph could easily be a screed against the president.
Combine that with the religious right's standard patter about "Christian America," and there's no question about it--the fundies are really using this to subvert religious freedom through the back door. After all, if someone can be denied office because his religious beliefs supposedly make it impossible for him to honestly take the oath, such a principle can only be enforced if you scrutinize which religions can "honestly" take the oath. If that isn't a religious test, what is?