Born Bad

''I may not be a good writer, but I write for a good reason,'' Vachss declares in his introduction to the collection of crime stories Born Bad. He's wrong. A former social worker and prison director who is now a lawyer, Vachss draws on his professional experience to write streetwise vignettes — but they're draped in a suffocating cloak of moral correctness. In exceptional tales like ''Bum's Rush'' — a murderer of the homeless learns to stalk his prey so effectively that he becomes what he hunts — Vachss wanders into the ethical gray zone in which he flourishes, sounding more like an inspired author than a literary parole officer. But too often his one-trick tales of revenge against child, wife, and animal abusers prove that good scruples don't make great stories. B-