Former President Donald Trump is once again doubling down on a flagrantly unconstitutional punishment for protesters, MSNBC legal journalist Jordan Rubin wrote on Thursday. He was referring to a Trump proposal of jail sentences for people who burn the American flag in response to anti-Israel protesters at the Democratic National Convention in Chicago — an idea he also suggested earlier this summer. It’s a suggestion that has been pushed by some on the right for decades but it’s not compatible with the Constitution, Rubin wrote. Want more breaking political news? Click for the latest headlines …