Every day when those of us who are parents say good-bye to our children, a little tooth of anxiety gnaws at us until we see them again. No matter how old or how mature they are, no matter how confident we are that we have prepared them for the traps the world sets, deep down we fear that something terrible will happen to those we love.

For one family of Riverdalians, the call every parent dreads came last week, when their 17-year-old son was waylaid, threatened, terrified, and humiliated in North Riverdale in broad daylight.

The young man wasn't mugged. What happened to him was far worse. He was attacked because of the color of his skin.

A middle-aged white man who claimed to be a police officer stopped the young man on Spencer Avenue by brandishing a gun. He pushed him up against a parked car, forcing him to assume the position of a suspected criminal, and peppered him with questions about what someone who looked like him would be doing in a neighborhood like North Riverdale (the neighborhood where the young man has lived all his life). "If you ever come into this neighborhood again," he threatened, "I'll kill you."

In a cry for justice addressed to Mayor Rudolph Giuliani, the young man's mother asks, "What are the leaders of this city going to do about restoring my son's confidence? What are we supposed to tell him after training him to respect all authority? Our son is a sensitive young man who celebrated the diversity of his community . . . What do we do for him now? He's afraid to walk in his own neighborhood."

Three and a half years ago, hoodlums assaulted a group of young Orthodox Jewish students at the 235th Street overpass, taunting them with epithets. Hundreds of residents flocked to a rally organized by Rabbi Avi Weiss of the Hebrew Institute two days later. Mayor David Dinkins dispatched the city's Human Rights Commissioner to express his concern. Borough President Fernando Ferrer, Councilwoman June Eisland, two members of the State Assembly, and representatives of Congressman Eliot Engel and mayoral candidate Rudolph Giuliani spoke. The clergy turned out in a body. The entire community made its revulsion at bigotry clear.

By contrast, virtual silence has greeted last week's incident. Councilwoman June Eisland and Assemblyman Jeffrey Dinowitz have contacted the family and expressed their outrage. After the young man's mother followed up her letter with a phone call, Bronx Borough President Fernando Ferrer's office called back. But at press time, nine days after the victim's mother appealed to the Mayor, neither he nor his police commissioner have responded. And no other community leader has come forward to voice concern or compassion.

As a community, we need to answer the young man's mother's questions. We need to assure her son that he is welcome here. We need to promise him that we won't assume a black man must be up to no good. In our homes and schools, we need to tell his story to our children, so that they'll understand that racism is not a phenomenon of America's past but a present threat to our own lives.

The thugs who assaulted this young man insulted all of us. They assumed we would applaud what they did, or at least regard it with indifference. Don't let our silence prove them right.