BROOKLYN - Nearly 200 people gathered yesterday in Manhattan to protest against NYPD's controversial "stop-and-frisk" policy.The tactic allows police officers to conduct street patdowns on individuals who are suspected of criminal activity. Opponents of the "stop-and-frisk" practice say it disproportionately targets blacks and Latinos in poor neighborhoods, often for no apparent reason.Demonstrator Tyrone Purvis says he was stopped and frisked once for crossing the street while the light was changing. The NYPD says its "stop-and-frisk" policy has led to a drop in street crime. About 30 people were arrested for disorderly conduct at yesterday's protest, according to police.