INTERVIEW : Brooklyn District Attorney Holds Reins on Beirut of the East : In a place where more than 800 people were killed last year, he says lessons of tolerance and goodwill are vital, even if some must learn the hard way. By John J. Goldman, TIMES NEW YORK BUREAU CHIEF. \o7 Brooklyn District Atty. Charles J. Hynes is an inner-city prosecutor under pressure. A 57-year-old veteran of the criminal justice system, Hynes rose to national prominence in 1987 when he successfully obtained convictions against members of the white teen-age mob that attacked three black men in the Howard Beach section of Queens and chased one of them, 23-year-old Michael Griffith, onto a busy highway, where he was killed by a car. Hynes spoke recently with Times New York Bureau Chief John J. Goldman in Hynes' office in Brooklyn's Municipal Building--a room decorated with memorabilia of his two years as New York City's Fire Commissioner\f7