THIS WEEK'S Political Cheap Shot Award goes to Rep. Claude Pepper (D-Fla.), who seized on a series of tragedies in the Washington area to give the District of Columbia's crack fire department the rubber-hose treatment on Capitol Hill-including calling the city's fire chief "a dumbbell." Pulling rank as chairman of the House Select Committee on Aging, Mr . Pepper summoned department officials to a hearing on recent fire deaths here and proceeded to conduct a nasty grilling-firing questions at them that, had he expressed any useful interest in this subject in the past, he would have known were misdirected.

Congressional bullying of the District is an old game, of course, but Mr. Pepper's run at it was especially cruel and ignorant. For one thing, there has been absolutely no evidence that this city's firefighters or their top officials had failed to enforce any codes or properly fight the two fires in which 10 elderly people died this month. In fact, the D.C. Fire Department is ranked nationally as one of the best, with one of the strongest fire-prevention codes. Had Mr. Pepper troubled to inform himself, he would have known that the problems have to do with other safety and inspection codes-and that the fire department has long supported the very kinds of safety measures and enforcement that the chairman is now calling for.

Instead of callinf for a grand jury investigation, Mr. Pepper and his committee collegues might also have checked to find out what Mayor Barry already was in the process of doing about fires. Among other things after ordering and receiving a detailed report on conditions in halfway houses and nursing homes, the mayor has directed subordinates to clear up all fire and health violations in the 27 city facilities for homeless, mentally retarded or incarcerated adults and children.

Mayor Barry also has publicly reprimanded Albert P. Russo, director of the Department of Human Resources, for failing to enforce regulations governing fire escapes, smoke detectors, fire doors, extinguishers, alarms, light system, wiring, handrails and the storage of drugs. The DHR director was cited, too, for "knowingly placing DHR clients in unlicensed facilities and for his failure to warn the Department of Health, Education and Welfare and St. Elizabeths Hospital that they were referring clients to unlicensed and unsafe D.C. facilities."

In addition, the mayor has suspended without pay for 90 days, demoted and transfeered the employee responsible for inspecting the Lamont Street fostercare home where nine female outpatients of St. Elizabeths died. And he has formed a group of city officials to get rid of the bureaucratic stumbling blocks.

Even with all these moves, the threat of still more grim incidents will not disappear, for there are other factors contributing to this danger. Not only are there more people from St. Elizabeths and Forest Haven now living around the city, but - as elsewhere in the nation-the population is older. Experts point out that the majority of fatal fires involves the very young, the very old and careless use of matches. In Washington and every other city, the challenge is to see to it that these two age groups are accommodated as comfortably and safely as possible. More than anyone, Mr. Pepper should understand these issues instead of trying to make a scapegoat of a dedicated group of firefighters.