A $5 million civil rights suit was filed in federal court yesterday against singer Anita Bryant and her anti-gay rights crusade, charging that it contributed to the slaying of a 33-year-old San Francisco homosexual, Robert Hillsborough.

Hillsborough, a city gardener, was beaten and fatally stabbed as he was returning home last Thursday. Four young men, including a 16-year-old, were arrested within a few days and charged with the murder.

Witnesses were quoted as saying that the four youths shouted "faggot, faggot"

and "here's one for Anita" during the attack.

The suit was filed by the victim's mother, Helen Hillsborough, 73, of San Diego, who said she had known about her son's homosexuality for six years and still loved him.