A Texas plumber has been receiving threats after a photo emerged of Islamic extremists in Syria firing a high-powered gun from the bed of his old pickup, which still bears his company’s logo on the door. An extremist group, Ansar al-Deen Front, posted the photo of its fighters aboard the Ford F-250 sometime on Monday. That prompted a flood of calls to Mark Oberholtzer, who owns Mark-1 Plumbing in Texas City, and has nothing to do with Syria’s bloody civil war. “How it ended up in Syria, I’ll never know,” Oberholtzer told The Galveston Daily News. …