A unit of the New York City Police Dept., with the assistance of the Motion Picture Assn. of America’s anti-piracy group, has arrested 75 peddlers of pirated videocassettes since the organization started cracking down on video piracy six months ago.Along with the arrests came the confiscation of 11,583 unauthorized copies of MPAA member-produced films. In addition to the tapes, the city’s Community Police on Patrol unit has taken in three vehicles, VCRs, televisions and other video duplication items. According to the MPAA, the confiscated tapes represent lost revenues to members of about $ 750,000. The CPOP unit’s most recent arrest was last Thursday and included the confiscation of 101 pirated tapes such as “Falling Down,”"Sniper,”"The Bodyguard” and “Malcolm X.” Throughout the city, street vendors regularly sell unauthorized copies of the latest theatricals. Indeed, the movies are usually available soon after they are released to theaters and sometimes before.