WHEN Democrat Frank Rizzo ran Philadelphia from the mayor's office in the 1970s, people called him a bully. A former cop and police commissioner in the late 1960s, Rizzo was renowned for using his power to bash those whom he once called "bleeding hearts, dangerous radicals, pinkos and faggots."

Rizzo did much to earn his reputation. As a cop, he came under attack from the ACLU in the 1950s for stopping interracial couples on the street for questioning. Later, the Justice Department investigated his department for police brutality, and many Philadelphia cops were indicted.

When riots were breaking out in many big cities in the late 1960's, Rizzo, often referred to as "America's toughtest cop," was determined to prevent them in Philadelphia. He once told Stokely Carmichael to "choose [his] words carefully" when the revolutionary civil rights leader came to the city to give a speech. He threatened, "I'm tellin' you, Mr. Carmichael, if you cause a riot in this town, I'm going to personally tear you apart. It'll take four orthopedic surgeons a week to put you together."

THOUGH Rizzo, who turned Republican to run in the last mayoral election after he lost the Democratic primary, has been out of office for nearly a decade, he's still throwing his hefty weight around in the City of Brotherly Love. After he lost last year's mayoral race to incumbent W. Wilson Goode, Rizzo became a talk show host on WCAU-AM, one of Philadelphia's highest profile radio talk stations.

The show has brought Rizzo national recognition. The former mayor earned a blurb in Time magazine. And earlier this week Rizzo found his way onto the front page of the Boston Globes's Living/Arts section in a full-page feature article.

While the sweet $100,000-a-year job might be a windfall for Rizzo, "Frank Talk" has got to be one of the biggest embarrassments for the city this decade. And that's a pretty tough feat considering the 1985 episode when Goode bombed a house owned by MOVE, a radical group, and burned down a whole city block to bring the city national notoriety.

So what makes Frank's show so bad? In a word, Frank.

For starters, the ex-Mayor isn't one of the most eloquent guys around. One Temple University communications professor claims that Rizzo "murders the English language." Rizzo punctuates his show with lots of South Philly "Yos," and the 68-year-old has little problem using his loud voice to over-power callers and ram his points home. Often he sounds like he'd silence his critics with a night stick if he had the chance.

Perhaps the style wouldn't be all that intolerable if Rizzo could actually come up with anything intelligent or informative to say. But the big guy fails when it comes to that part too.

RIZZO has so little interesting to say that he spends most of his time taking cheap shots at Goode, his current political nemesis. He has called the mayor an "ingrate" and says he can't tell the "truth." Rizzo ends every single show with the threatening line, "And good night, Wilson, wherever you are."

During the rare times he doesn't criticize Goode, Rizzo takes aim at some of the other liberals he so dislikes. He interviewed author Leo Damore about his book on Senator Edward M. Kennedy (D-Mass.) and Chappaquiddick and afterwards called the work "one of the best books I ever read." One can only imagine what other good literature Rizzo has taken in lately.

WCAU, usually a quality station, has stooped to the lowest levels by giving Rizzo access to the airwaves. While talk radio is quickly becoming a legitimate and potent political force, Rizzo's tough talk and thinly disguised bigotry adds nearly nothing to the city's political dialogue. The little it does add convincingly demonstrates why Rizzo lost the election to Goode, who was widely perceived as ineffective and incompetent.

Of course, even though Rizzo is a demagogic liberal basher, he deserves his freedom of speech. And WCAU, as a business, can do whatever it wants to bring the station what recently hired station manager Gregory Tantum termed a needed "higher profile."

But WCAU should recognize its professional repsonsibility to give the public programs of quality and should make Rizzo find another way to reach what he calls the "rowhouse people, the little people." Rizzo's show amounts to little more than a bully pulpit from which this incessant politician can launch another bid for the mayor's office and embarrass Philadelphia more.

Hey, Yo, WCAU, enough already.