I am an informant and all I can tell you is that Talibans are walking freely right here in the soil of America right now, right now.” That’s the haunting worry of South Floridian David Mahmood Siddiqui. He was the confidential FBI informant who has a rare view of of trying to infiltrate a largely secreted world of what the U.S. government considers terrorist sympathizers. Asked by Gillen what he thinks the risk of having Taliban living in America is, he responded; “They can commit a jihad at any time, they hate America, you have an enemy living here in...