THE audio tapes of Los Angeles policeman Mark Fuhrman are igniting the most heated debate on racism in law-enforcement ranks since the clubbing of Rodney King nearly five years ago. Coming on the heels of evidence of bigotry by rogue officers in Philadelphia and allegations of abuse in several other big-city departments, the tapes are spurring a renewed look at police conduct nationwide. Police defenders argue that a few bad officers shouldn't be used as a yardstick for all the nation's men and women in blue. But critics contend the comments on the tapes are indicative of entrenched racism in forces throughout the country - indeed, the entire criminal justice system - and that little progress is being made in ridding the institutions of racial sentiments. Tapes spark dialogue To many of these detractors, though, the Fuhrman furor could end up having a salutary effect, to the extent that it prompts a reassessment of police behavior. Others worry the incendiary tapes will only inflame police-public sensitivities at a time when many ethnically diverse cities are poised to erupt in violence. ''This is the best thing that could happen for American public education about its police departments,'' says Mary Powers, chief coordinator for the National Coalition for Police Accountability. Formed in the wake of the Rodney King beating, the Chicago-based NCPA is seeing a major surge of interest for its fifth annual meeting next month, she says. Mark Whitlock is more wary. ''I have mixed emotions about the airing of so much racist diatribe that could possibly inflame our city,'' counters the black activist with the First African Methodist Episcopal Church in South Central Los Angeles. Though he agrees that the tapes help raise public consciousness about long-entrenched attitudes that need exposing, he says: ''I don't believe violence is a good way to induce change here, but I certainly see its potential on the heels of this.'' The tapes were recorded by screenwriter Laura Hart McKinny as research for a film about sexism in the LAPD. Played in court (but not for the jury) for the first time last week, the tapes reveal that Officer Fuhrman used a racial epithet 41 times and made disparaging comments toward blacks in all walks of life, including members of the Los Angeles City Council. ''The Fuhrman tapes are revolting,'' said Los Angeles Urban League President John Mack. ''They confirm in the minds of most African-Americans what we knew all along: that Mark Fuhrman and what he represents amount to the worst in law enforcement.'' Fuhrman also boasted of fabricating evidence and making denigrating remarks about the racial makeup of one largely black division of the LAPD. ''The Fuhrman episode has every potential of exceeding the Rodney King beating, two subsequent trials, and the riots as a mechanism to focus attention on racism within police departments,'' says James Fyfe, criminologist at Temple University in Philadelphia. ''It underlines in red ink that constant public scrutiny of police is a must.'' National moves to clean up racism and other abuses among the nation's 650,000 police officers have not been sustained since the beating of Mr. King, critics say. Calls for citizen review boards, community policing, cultural and racial sensitivity training, have resulted in more talk than substantive change, they say. ''We have found that there are no quick solutions to such racial attitudes,'' says Nancy Rhodes, editor of Policing by Consent, the newsletter of the NCPA in Syracuse, N.Y. ''We hear all the time that despite training in an academy setting, officers revert back to previous behavior when they get back to the 'real world' of their beats.'' Data show that citizen review boards have grown in number since 1991 to about 100 nationwide and have had positive effects. But, observers say, they are constantly fighting with authorities over legal power and funding. Boards in Dade County, Fla.; Los Angeles, San Francisco, and Syracuse have lost money and clout in the past two years. And the San Diego law-enforcement review board, formed in the wake of the King trials, was informed by the county board of supervisors Aug. 14, that its $308,500 yearly budget will be cut in half. The Fuhrman tapes actually may help forestall moves to dismantle boards or deprive them of funds, according to the NCPA. Their consciousness-raising value comes from the fact that Fuhrman's comments are not unusual, activists say. ''The shock and outrage I have heard [over the tapes] shows most people don't know what is common in police departments across this country,'' Powers says. LAPD Blues In Los Angeles, the LAPD is under renewed scrutiny, further straining relations between public, police, and politicians. Here, where Christopher Commission investigations led to a public initiative for police reforms, new laws have lacked teeth. Observers blame a lack of police commission support by Mayor Richard Riordan as well as the entrenched racist culture of the LAPD. ''The Los Angeles police have been in a state of open mutiny to reform since the first calls to change,'' says Los Angeles historian Mike Davis. ''Changing the man at the top without letting him appoint his own top deputies is like asking Ronald Reagan to be president using Jimmy Carter's Cabinet members.''