The thing to remember about the Republicans in Deep South states like Alabama and Mississippi is that they are mostly older, lily white, and very conservative. When you combine that with racial stratification and lingering resentment, it's easy to see how 21 percent of Alabama Republicans and 29 percent of Mississippi Republicans would say that interracial marriage should be illegal, according to the latest poll from Public Policy Polling. Likewise, given the extent to which anti-Islam prejudice has made "Muslim" a stand-in for certain racial slurs, it's not hard to see why 52 percent of Mississippi Republicans and 45 percent of Alabama Republicans would say that the president is a Muslim.
In fairness to Republicans in both states, the GOP as a whole has a problem with correctly identifying Barack Obama's place of birth. According to a January poll from YouGov, 37 percent of Republicans deny that Obama was born in the United States, while 35 percent aren't sure:
This comes after the president released his long-form birth certificate in a highly publicized announcement.
In other words, you can't say that this is a surprise.