The white cop dragged the black suspect to the bathroom. He crammed a plunger handle into his rectum. He slammed it into his mouth, severely enough to break teeth. Meanwhile, the cop spoke about, of all things, politics. "This is Giuliani time," the victim remembers the cop saying, "not Dinkins time."

Like everyone else, I was repulsed by this now widely known obscene attack on Aug. 9 on a Haitian Immigrant by New York City police officers, but I can't say I was totally surprised. The political talk didn't surprise me either. Over four decades in law enforcement, especially in my years running an urban department formerly renowned for its brutality, I came to learn how directly the message of a mayor or a police chief drives the actions of cops.

To some, it may seem unfair to tar New York Mayor Rudolph Giuliani with the comments of an out-of-control, violent cop. Giuliani never told his cops: Go beat up suspects.

But he did turn them loose, and he knew the consequences. Like much of America, New York City has become a more violent place -- thanks to violent cops, not criminals on the streets -- because its top politician ushered in an intimidating atmosphere of "zero tolerance." Of harassing squeegee guys who clean windshields at highway exits. Of joining the national crusade to turn law enforcement into a domestic "war."

Giuliani speaks like a general who wants to wipe out subhumans -- so it's no surprise his cops behave like soldiers devouring the enemy.

Rude Rudy is hardly the only official speaking this way. The political culture of "crackdown" shares the blame for a wholesale attack on the constitutional rights of criminal suspects and of just plain everyday people who happen to live in poor neighborhoods, or black or Latino neighborhoods, or neighborhoods where drugs are sold. Stories emerge almost daily of allegations of unwarranted violence against civilians by agents of local or national law enforcement.

Police brutality always comes in waves. It's up now because of the tone our politicians have set in order to pander to voters' fears about crime and their demands for short-term drops in crime rates.

All police forces have their adventure-seekers, people drawn to the work by the lure of violence, of power, of control over the weak. Leadership can keep those people largely in check by sending out a message that such behavior won't be tolerated and by bringing wrongdoers up on charges.

Or leadership can unleash them.

Most cops are not by nature violent. But like most people, they want to please the boss to get ahead. They want to be detectives they want to be sergeants, lieutenants, captains -- and so they respond to the tone their leader sets, the expectations set.

Any law enforcement veteran understands that telling cops to "get tough" means you will exchange people's civil liberties, their right to humane and respectful treatment, for short-term declines in crime statistics. Any prosecutor -- including former prosecutor Giuliani -- understands that, too.

That approach wins votes in the short term. Over the long term -- as we now see in New York, as we will see in Los Angeles -- you lose the support of too many people in the community.

Yes, some people want the mayors and police chiefs to keep "them" -- the poor people, homeless, mentally ill people, drug addicts, blacks and Latinos, gays and lesbians -- out of their communities. But you can't wish or bully differences or problems away.

Ultimately, law enforcement that is unlawful can't succeed. Without the support of the disenfranchised -- as well as the law-abiding people in troubled areas trusting the cops enough to cooperate in building strong, intelligent cases against criminals and in creating alternatives to crime -- we will all lose. Even criminals need to trust cops' fairness.

After elections pass, two-thirds of the people we incarcerate return to the streets. Do we expect them to act like law-abiding citizens after we have extensively demonized or dehumanized them?

Giuliani did appoint a commission on brutality in the wake of the plunger incident, his apologists point out.

But where was that commission while brutality complaints piled up like cancerous sores on the body politic over the last three years?