Hundreds of protesters rallied outside Canarsie’s 69th Police Precinct on Thursday to demand answers after a viral video captured police officers tackling 20-year-old Fitzroy Gayle to the ground during an arrest for alleged marijuana possession. “We had a rally outside of the precinct calling on the District Attorney of Brooklyn to investigate this heinous kidnapping and assault,” said Rev. Kevin McCall of the Crisis Action Center in Brownsville.  Video captured and posted to Twitter Thursday morning showed a plainclothes officer holding Gayle at gunpoint before a swarm of police brutally tackle him to the ground. In the video, …