Sensible people may live to bless Gramm-Rudman-Hollings, the crazy budget-cutting contraption recently installed on Capitol Hill by people who admit they can't cut the budget without the help of a mechanical arm on the ax.

The damage it will do to domestic programs has been amply documented in recent weeks. But its peaceful uses may be appreciated if it can foil some of the preposterous foreign adventures put forward by President Reagan.

Take, for instance, the campaign to resume financing of Angolan guerrilla Jonas Savimbi, who is in town peddling "democracy" for his native country. Aid to the Angolan rebels was outlawed in 1975 by the so-called Clark Amendment, which put Angola off-limits after a clumsy CIA intervention there failed. (Last year, Congress repealed the Clark Amendment.)

But Reagan and his far-right followers, deprived of the thrill of direct anticommunist action, passionately promote proxy wars against Angola and Nicaragua, seeking to fill rebel war chests in both countries.

The Angola policy goes against reason, history -- and U.S. business interests. David Rockefeller, for one, is vigorously opposed. But the Reaganites think that funding Savimbi will somehow result in the withdrawal of the Cuban troops who were brought in to save the government from defeat by the guerillas -- and stayed on to guard the Chevron/Gulf Oil installations, which are periodically sabotaged by Savimbi and his South African allies.

Savimbi, a big, handsome, round-eyed opportunist, is making the rounds in Washington under the auspices of one of its high-powered public relations firms, Black, Manafort, Stone and Kelly, which is charging him $600,000 for changing his image and his prospects. If plans for some $15 million in aid succeed, American taxpayers will have the dubious pleasure of helping pay the bill for being conned.

Savimbi did well at the White House with President Reagan, who promised him "the most effective aid" he could. He is being lionized by the far right.

At the Conservative Political Action Conference banquet last week, former U.N. ambassador Jeane J. Kirkpatrick introduced him as "one of the few authentic heroes of our time."

To others, he appears more like a character in one of those darkly satiric African novels by Evelyn Waugh. The conservatives' favorite "freedom fighter" was trained in guerrilla warfare in communist China, and at one time in his life was more antiwhite than antired. But his media chaperones have taught him to profess a mania for democracy.

In a breakfast visit with Washington Post editors and writers, Savimbi demonstrated considerable swagger. He said that the Gulf Oil Company (now part of Chevron), which has been getting along just fine with the Marxist rulers of Angola, would have to stop lobbying against his cause if it doesn't want to get blown up by his forces.

He also said he would not send a diplomatic representative to South Africa unless it abandoned apartheid. Other black states regard Savimbi as the puppet of the South Africans.

The administration once wanted to negotiate an end to the region's impasse, seeking the simultaneous withdrawal of Cuban troops from Angola and South African troops from neighboring Namibia. But these efforts were apparently dumped when the president backed aid to Savimbi, saying he would prefer the covert kind. It may be his way of expressing resentment at being forced to impose sanctions on South Africa.

Congress is bracing for his call to arms. Can it oppose funding "freedom fighters" and beat the "soft on communism" rap? Gramm-Rudman-Hollings is the only alibi in sight.

The administration defiantly proposes about $100 million for the faltering Nicaraguan contras. By starting the bidding high, it hopes to get a minimum $30 million in humanitarian aid and perhaps the same amount or more for lethal stuff. There, as well, it has spurned negotiations. The Contadora countries, which seek a nonviolent settlement, have been put down hard.

Many Democrats agonize that they cannot get away with voting against both Savimbi and the contras. The one thing that may stiffen them is the thought of having to cut schools and playgrounds in their home districts -- and, for heaven's sake, their own staffs.

It is possible that in the coming debates, we will see people diving for the cover of Gramm-Rudman-Hollings, professing a militant anticommunism while turning out their pockets to show there is nothing there to finance "the march of folly" abroad.