A scandal of potentially titanic proportions is brewing at the Federal Emergency Management Agency. Last week, FEMA administrator Deanne Criswell fired Marn’i Washington, the official accused of discriminating against Donald Trump-supporting hurricane victims in Florida, casting her as a lone wolf, a bad apple in an orchard full of good ones. Not so fast. On Tuesday, Washington — and another ex-FEMA employee who spoke with The Post — disputed the relatively rosy picture painted by Criswell. According to the recently disgraced Washington, “FEMA preaches avoidance” from potentially contentious situations. And, supposedly, Trump supporters are disproportionately responsible for fomenting such situations....