An Adams administration staffer whose mission includes fostering “unity” and bridging “cultural divides,” is under fire for ripping down an Israeli hostage poster — and then allegedly assaulting an outraged eyewitness, The Post has learned. Nallah Sutherland, a special event coordinator for the Mayor’s Office of Special Projects and Community Events, was spotted earlier this month tearing down the poster from an Upper East Side light pole, ripping it up and dumping it in a trash bin, according to video posted online by the nonprofit StopAntisemetism.