JOHN KASS What exactly triggered that hateful leftist social media mob — shamefully egged on by prominent American journalists — to unjustly attack the students at Kentucky’s Covington Catholic High School and denounce them as racists? The school has been closed. Death threats and bullying continue. Students and family complain they’ve been doxed — their identities revealed so that the hateful mob can harass them some more. So, what happened? Why were the students vilified? Was it simply for the sin of being white, Roman Catholic supporters of President Donald…