A New Jersey educator is in hot water because of a tape he used to show seven youths, aged 15 to 17, how to prevent the spread of AIDS. The tape, which urges the use of condoms, was produced by the Gay Men's Health Crisis in New York City. It also happens to include scenes of gay men having oral and anal sex. \n Keith Carson, 32, an AIDS prevention educator for the South Jersey AIDS Alliance, has been charged recently with distributing obscenity to minors. If convicted, he could be imprisoned for up to 18 months. \n The Cape May County prosecutor said the 25-minute video was inappropriate for educating young teens. \n Carson's own employer, the South Jersey AIDS Alliance, appears to agree. The alliance had not approved the tape for presentation to youngsters and has disciplined Carson for showing it last February. Bill Mattle, executive director, said he does not believe Carson meant any harm but only used poor judgment. Mattle would not say how Carson has been punished but he confirmed that Carson remains on the staff. \n The American Civil Liberties Union has entered the case on Carson's side. The ACLU said showing the tape is protected under the First Amendment. The tape was intended to educate the teens, not to titillate them, said David Rocah, who is representing Carson. If Carson is convicted, it will chill efforts to educate students about the dangers of AIDS and how to prevent it, he said. \n Rocah also said he was concerned about a situation in which a prosecutor with no training in education can second-guess a trained educator concerning which materials are appropriate for the instruction of teens.