President Barack Obama dismissed a recent poll showing that a third of Americans don’t know he’s a Christian – and blamed an online campaign of misinformation by his conservative enemies for perpetuating the myth that he’s a Muslim. “I can’t spend all of my time with my birth certificate plastered on my forehead,” Obama told NBC Nightly News anchor Brian Williams, sitting under a tent in a rain-soaked New Orleans, where he commemorated the fifth anniversary of Hurricane Katrina. “The facts are the facts. We went through some of this during the campaign — there is a mechanism, a network...