Remember Henry Kissinger's celebrated "tilt" toward South Africa? That early 1970s policy, which President Nixon bought, called for a public "modest" increase in U.S. aid to black Africa while secretly increasing ties between the United States and the South African government.

It sounded pretty dreadful at the time. Today, in comparison with what the Reagan administration is doing, it sounds downright moderate.

What is happening now is no secret "tilt." It is turning long-term U.S. policy toward South African completely, and blatantly, upside down.

Reagan has been warming up to the world's most widely condemned racist regime virtually since he took office. Last week, after South Africa invaded Angola, the United States split with its major allies and vetoed a U.N. Security Council resolution that would have condemned South Africa for the invasion.

"The Reagan administration has no intention of destablizing South Africa in order to curry favor elsewhere," Chester Crocker, assistant secretary of state for African affairs, explained.

It isn't clear how an official condemnation of military adventurism would "destablize" South Africa--any more than Israel was destablized when the Security Council, with a "yes" vote from U.N. Ambassador Jeane Kirkpatrick, condemned the Israeli attack on an Iraqi nuclear installation.

The official U.S. position was that the Israeli bombing raid was comparable to the Soviet invasion of Afghanistan, so "shocking" that America joined in the 15-0 Security Council vote against its longtime ally. The raid undercut peace efforts in the region, we said.

The unresolved mystery is why the Reagan administration was not shocked by the South African foray into Angola or why it does not see the invasion as undercutting peace efforts in that region.

For years, South Africa has been resisting a U.N. mandate to relinquish its control over neighboring Namibia (South West Africa). The official rationale for last week's raid was to chase down and destory "communist-supported terrorists" of the South West Africa People's Organization, that has been fighting South African troops for 16 years for control of Namibia. South Africa's administrative control of Namibia was declared illegal by the United Nations in 1965.

SWAPO is recognized throughout black Africa as the sole legitimate representative of the Namibian people and, in the Western world, as at least one legitimate voice.

The Reagan administration apparently believes that its kid-glove handling of South Africa will enhance its ability to move South African toward a Namibian settlement. What seems far likelier is that South Africa will be encouraged in its efforts to hang on in Namibia until it can discredit SWAPO and deny it a role in governing an independent Namibia.

South Africa, for its part, seems to be counting on the administration's tunnel- visioned anti-communism to turn it against SWAPO. Thus, the South Africans have made a big deal of the fact that three or four Russians were among those killed or captured in the Angolan "incursion," stressing their hope that "the Western world will take serious note of this and that this evidence will lead to a more balanced approach by the Western powers."

But the presence of Russians--and East Germans and Cubans--in Angola has never been a secret. What the South African raid has done is to lend legitimacy to Angolan claims that they need communist support to help defend themselves against South Africa. It also puts the Soviets in the good guy role against the South African racists.

None of this can serve the interests of the United States, which seems well on its way to destroying its credibility in much of the world, including all of black Africa, while gaining nothing of substance in return.

It is true, as Assistant Secretary Crocker said, that America does billions of dollars worth of business in South Africa, much of it in vital minerals. But that commerce is not in apparent jeopardy. Indeed, South Africa has been glad to have the business while enduring U.S. criticism of its racist policies.

Crocker, who knows that, knows something else as well, as The New York Times reminded him in an editorial last Thursday:

"As a multi-racial democracy, the United States cannot endorse a system that is racist in purpose or effect. . . . Pressure for change should be a central ingredient in American policy, and that pressure must be credibly maintained if we are not to send misleading signals to South Africa."

That clear statement, which appeared last year in an article in Foreign Affairs magazine, was written by Chester Crocker, who now undertakes to justify the relaxation of "pressure for change."

The problem is not that Crocker's irreconcilable statements paint him as inconsistent. The problem is that the Reagan administration's South African policy puts America in jeopardy of landing on the wrong side of yet another struggle against oppression--and once again in the name of anti-communism. it in vital minerals. But that commerce is not in apparent jeopardy. Indeed, South Africa has been glad to have the business while enduring U.S. criticism of its racist policies.

Crocker, who knows that, knows something else as well, as The New York Times reminded him in an editorial last Thursday:

"As a multi-racial democracy, the United States cannot endorse a system that is racist in purpose or effect. . . . Pressure for change should be a central ingredient in American policy, and that pressure must be credibly maintained if we are not to send misleading signals to South Africa."

That clear statement, which appeared last year in an article in Foreign Affairs magazine, was written by Chester Crocker, who now undertakes to justify the relaxation of "pressure for change."

The problem is not that Crocker's irreconcilable statements paint him as inconsistent. The problem is that the Reagan administration's South African policy puts America in jeopardy of landing on the wrong side of yet another struggle against oppression--and once again in the name of anti-communism.