Dresed in white, the color of angels, and wearing their piety like a war ribbon, the generals, admirals, colonels and captains of the Argentine military strode into St. Matthew's cathedral. Along with embassy officials, the crew that represents Argentina's junta was coming to a special mass held for them last Friday as part of the celebration for their country's national day.

These doings were part of an old story: Catholicism's calculated coziness with pagan governments that rule by violence and fear. Since November 1974, the Argentine military junta has abducted thousands of citizens and sent them off without trace to prison camps or to death.Thousands more are detained in jail without charge or trial. Amnesty International, along with other groups, had documented the repression.

Tyranny doesn't look so bad when it kneels in a holy place and is given respectability by so grand a tribunal as the Archdiocese of Washington.

These special masses have been held in other years for the embassy. It is sterling public relations for a junta's high-powered thugs to be received with pomp in a great cathedral in a world capital. The spectacle will lead the uninformed to assume that all is well in Argentina; otherwise, why would the American church be so embracing?

That would have been the story, except that what the junta proposed God didn't dispose. The celebrant of the mass, the Rev. Sean O'Malley of the archdiocese social development office, delivered a sermon that drove the congregation of 300 from the church. O'Malley's offensiveness was to relate scripture and the thoughts of Pope John Paul II on social justice to the current brutality of the Videla government. He cited Jeremiah and referred to Herod's slaughter of the innocents.

The Argentine exodus took but a few minutes. With one highranking general leaving first, the underlings followed. In the pulpit the priest kept to his text.

Outside, the military men were damning him for "turning a religious event into a political one."

Another of the white-suited contingent, looking as furious as St. George hot to slay a dragon, said that "priests have no place in politics. He should have given a sermon an another subject, like the love of God."

As the pouting group drifted off to a reception at the embassy - where things would go better, without this troublesome priest on hand - the institutional church did itself well, however unintentionally. It would have been better if the archdiocese had barred these tyrants in the first place, based on the scriptural command for believers to make peace with their brothers and sisters and then come to the altar in reconciliation.

It is true that Catholicism presents itself as a church of sinners that has room for everyone. But in the theology of redemption, it has been understood that the sinners must display at least some measure of repentence. The junta's Washington delegation, posturing as defenders of virtue against subversives who attack the established order, saw itself in St. Matthew's as being sinned against. It was the priest who needed to repent. This attitude was in line with the statement last year of Argentine President Jorge Rafael Videla:

"A terrorist is not just someone with a gun or bomb, but also someone who spreads ideas that are contrary to western civilization."

The terror of O'Malley's sermon was bad enough for the Argentines but before the mass begain another attack on the West was made. The Rev. Patrick Rice, an Irish missionary who did pastoral work for six years in a Buenos Aires shantytown known as Villa Miseria, walked into the sanctuary and begain speaking. He told of his imprisonment and torture for two months, and of priest friends who disappeared three years ago.

Rice was about to ask that the Argentines in the cathedral join him in prayer for reconcilitation. But the organist drowned him out and the microphone went dead. Then the rector of the cathedral, a monsignor, appeared and told the young priest to move on.

He did, but not before looking to his right where six of his friends, including two nuns, stood with a peace banner in protest of Argentina's policy of torture. Quickly, a phalanx of District of Columbia police came up the aisle and ordered the demonstrators out of the church. Others in the pews were told to go. All went peacefully.

It was a chilling scene. A mass for the police state of Argentina needed to be protected from some docile Christian demonstrators by the police of Washington. A state of siege came to St. Matthew's. "The monsignor called us," said one of the officers, "and we came."

In keeping the scene calm so the prayers of the dignitaries would not be disturbed, the police looked the other way when members of the embassy goon squad punched some of the demonstrators and belligerently yanked cloth hoods from the heads of some of the others.

After the mass, Rice, who belongs to an order in which the clergy work for wages in the same factories and fields as the poor to whom they minister, said that he expected to be hustled out of the sanctuary. What he didn't expect, though, and became elated about, was the strong sermon. "In Argentina," he said, "few people have much hope in the church because they see it lined up with the government. They see a strong military vicariate, with large numbers of priests working for the government as military chaplains.

"Videla presents himself as an upstanding Catholic family man, with a private chapel near his office. The junta persuades the church to be a bulwark against communism. Anyone who tried to help or organize the poor, or has ideas the military objects to, is branded a subversive. Anything goes - death or torture - to stop him."

Rice's own story of suffering from electric shocks administered by a secret interrogation group has been documented by Amnesty International. When asked about AI, an Argentine officer said outside of St. Matthew's, "They're just liars." As for Rice, he reports that on the sidewalk he was called a Jew by one Embassy official and told that he would be murdered if he returned to Buenos Aires.

Word is likely to get back to the Argentina prison camps that at least two priests in Washington dared confront the fake piety of the junta. The unpleasant truths presented by O'Mally and Rice won't release any of the 4,000 to 6,000 people who Amnesty International estimates are being brutalized for political reasons. But it may ease some of the victims' painful sense of isolation.

To know that outsiders are on to the junta's violence - despite the public masses and white suits - offers some comfort. It is to believe that the moral arguments of the church may yet drive the corrupt not only from the pews but also from power.