So what does a bunch of federal bureaucrats know about Art?

Only that when it comes to a 73-ton, 120-foot-long, 12-foot-high wall of graffiti-scarred, rusted steel, planted on a plaza in front of their offices, they can do without.

No matter that the highest muckety-mucks of the international art world have swarmed to the defense of sculptor Richard Serra's "Tilted Arc." To bookkeepers, secretaries, judges and lawyers who work in the complex of government buildings around Foley Square in downtown Manhattan, the sculpture is "ominous," "arrogant," "pro-terrorist," "an eyesore," an "iron curtain."

This battle of esthetics, posing as a clash between elitism and populism, went public today as a three-day hearing opened here to explore whether the controversial sculpture, installed in 1981 as part of the General Services Administration's Art-in-Architecture program, should be removed.

The case, which will ultimately be decided at GSA headquarters in Washington, is being viewed around the country as a precedent-setting test of the federal government's commitment to sponsor contemporary art in public buildings. Over the past two decades, GSA has commissioned more than 200 such works of art and, while several have become controversial, none has sparked as concerted and heated an opposition as "Tilted Arc."

"The issue is whether or not the government can destroy a work of art it has commissioned," said Serra, an internationally known sculptor and a leader among avant-garde artists for the past decade.

Dismissing the opposition with a wave of his hand, Serra declared, "This isn't democracy, it's a lynch mob. A panel of government experts chose me. The government shouldn't be asking people about esthetics. This is censorship of creative expression."

The work, for which the GSA paid $175,000, has sparked protests ever since it was installed. Petition drives were mounted among the 10,000 federal employes housed in the high-rise Jacob K. Javits federal building and in the U.S. Court of International Trade, which loom above the sculpture. In the past few weeks, a questionnaire in the lobby of the Javits building produced 2,496 signatures in favor of removing the sculpture and 166 opposed.

Nor have the critics been kind. New York Times art critic Grace Glueck recently called "Tilted Arc" "one of the ugliest pieces of public art in the city, a domineering work that bullies rather than enhances the open plaza." Michael Sorkin of The Village Voice this week dubbed it a "superficial, schematic response, another dull sibling from a generation of too easy art . . . Minimal art mocking minimal architecture."

Neither, however, endorsed the drastic step of removal, which would cost GSA $60,000. "The troubling question is who gets trashed next," Sorkin said.

Thus, a battery of big-name artists turned out at today's hearing -- along with about 300 members of the public, divided into applauding claques and duly recorded by a host of local and network television cameras.

"Neither in this time nor any time in the past can art be defined by everybody," said sculptor Claes Oldenburg, decrying the efforts of "vigilante-type" opponents to "override the opinions of better-qualified persons . . . Taking a poll is no way to judge whether a work of art should survive."

George Sugarman, whose colorful abstract sculpture, "Baltimore Federal," caused an uproar in Baltimore a few years ago when angry judges claimed it would harbor rapists and muggers, also came to Serra's defense. Noting somewhat disdainfully that "Tilted Arc" might "not appeal to a TV taste or a McDonald's hamburger quick taste," he suggested that the public must "live with art to understand it."

Philip Glass, the composer, charged that "an attack on artistic freedom is a political act pure and simple and must be resisted."

Joan Mondale, a longtime patron of the arts, also has jumped into the fray and has volunteered to testify Wednesday for Serra. "Art is sometimes misunderstood by people who see it for the first time," she wrote the GSA. "We should wait to determine its eloquence and its eternity. Remember the Eiffel Tower in Paris? It was considered ugly and demands were made to tear it down. Now it stands as the symbol of the city."

Marion Javits, another arts patron, read a statement from her husband, former senator Javits, for whom the building is named. Noting that Picasso's "Guernica" was "neither likable nor pleasing," Javits said removing the sculpture would compromise "the kind of integrity which makes art in our society the symbol of what freedom means in the world."

Standing up to the art world elite, a gray-suited phalanx of federal judges and clerks, agency administrators and midlevel bureaucrats gave the project a thumbs down.

William Toby, regional administrator of the Health Care Financing Administration: "I . . . recommend its relocation to a better site -- a metal salvage yard . . . During my 17 years of employment in this building, nothing has offended me and my staff more . . ."

William Tucker, lawyer, Environmental Protection Agency: "This sculpture functions in a physically intrusive and confrontational way."

Gregory W. Carmen, U.S. Court of International Trade judge and former New York congressman: "Depressing and overbearing . . . Transients have been seen urinating on the 'Arc.' "

Bernard M. Kilbourn, regional director of the Department of Health and Human Services: " 'Tilted Arc' has been a magnet for ethnic graffiti. Racial and religious epithets abound on it . . . It is interesting to note that the federal building itself is graffiti-free."

Joseph Lombardi, court clerk: "a symbol of artistic noblesse oblige."

At times, it seemed as if critics and advocates were speaking different languages. "This newly created concave volume has a silent amplitude which magnifies your awareness of yourself and the sculptoral field of the space," Serra explained. "Understanding the simple distinction between a plane leading toward you that is curved and concave, and a plane leaning away from you that is curved and convex, is crucial. This establishes new meanings among things."

William Rubin, director of painting and sculpture at the Museum of Modern Art, which is mounting a major Serra retrospective next year, noted, "I must say that I have never heard of the removal of public monuments having been settled by popular vote, if that is what is being contemplated here -- and it seems to me a most dangerous precedent."

Although Serra, who lives in nearby SoHo, said he has collected 3,500 signatures in favor of the sculpture, residents of lower Manhattan are deeply divided. "The community -- those thousands of people who live and work in the area -- have a right to reclaim this small oasis for the respite and relaxation for which it was intended," said Rep. Ted Weiss (D-N.Y.).

Louise K. Reisman, a retired secretary, spoke on behalf of residents of a nearby middle-income housing project. "How few of us have roomy apartments," she said. "How many feel the need for space, vistas and horizons . . . This piece gives us ulcers -- not esthetic pleasure. There is no idea, no humor, no educational value. It looks barren. It is barren."

While Serra said it is an illegal violation of his contract for GSA to even contemplate removal, regional administrator William Diamond, who has been sharply critical of the work, said, "We strongly believe that the public has a right to tell us how they feel about the way in which their government spends their money." Diamond said he and a panel of four experts will make a recommendation to the new GSA administrator in Washington. The decision, he said, is expected within two months.