Sen. J.D. Vance threw an insult at Vice President Kamala Harris Tuesday that almost immediately boomeranged. Former President Donald Trump’s running mate took to X to accuse Harris of “flip-flopping” on her border security policy positions ahead of the presidential election in November — then faced stern reprimand from a fellow Republican. “Kamala Harris is a fake,” wrote Vance. “If she wants to build the border wall, she could start right now!” Want more breaking political news? Click for the latest headlines at Raw Story. Vance shared an Axios report that described Harris’ support of a bipar…