It's become pretty clear it was sarcasm. A reader writes:

He was LAUGHING at y'all in his third hour. "Obama was the only one who knew proper Muslim ritual for handing Bin Laden's body," Limbaugh told his audience.

Another writes:

Watch it again, my friend.  When Rush says "It was Obama alone" it gets really obvious what he is trying to do.  And what he is trying to do makes him as unpatriotic as any relevant American I've ever known.  Jane Fonda looks like Pat Tillman next to this odious pig.