Show us the post where a Freeper called the little Marxist squirrel the anti-Christ, then perhaps we’ll discuss it with you.
There have actually been quite a few, though it's certainly not a widespread belief among FR posters. To check for yourself, go to Google Advanced Search, type freerepublic.com in the "Search within a site or domain" box, and type the phrase (without quote marks) "Obama is the anti-Christ" in the "this exact wording or phrase" box. Of course that only picks up the ones phrased exactly way (surely plenty more are phrased slightly differently), and also picks up that phrase where it is immediately preceded by "I don't think that" or "I don't believe that". But quite a few hits from that search are indeed FReepers asserting that they believe Obama is the anti-Christ.
Seriously? If you REALLY want me to spend the time, I can take ten minutes to gather you fifteen quotes from any of the twenty post-election threads that contain the quote “I’m concerned that Obama is the antichrist!” If you truly are convinced that’s not the case, I invite you to re-read those threads.....you’re missing a whole lot of interesting theology.