The Iowa man who challenged Joe Biden during a campaign event on Thursday told The Post he had no regrets about the heated exchange. “I’m positive 90% of the people there didn’t know about his son working on the board in Ukraine. I wanted it brought out there,” said 83-year-old Merle Gorman, referring to Biden’s son Hunter’s job at a Ukrainian gas company. “If it educated them a little bit, so be it,” Gorman said. “I’m glad it happened.” During a routine campaign stop in New Hampton, Gorman set the former vice president off when he accused him of sending...