For a few rare moments, the decency of America and the bravery of El Salvador were on view for Congress.

Jack Elder, the director of Casa Romero in San Benito, Tex., where 140 Salvadorans a month are given food, shelter and dignity, had come to support proposed legislation to halt temporarily the deportation of Salvadorans now in the United States.

Next to Elder at the hearings was a young Salvadoran woman. To protect her identity from the U.S. Immigration and Naturalization Service, she wore a farmer's bandanna over part of her face. Well-spoken and with soulful eyes, she told Congress what most members already knew: "If I go back to El Salvador, I will be killed."

Rep. Joe Moakley (D-Mass.) was able to move the legislation out of his committee. But then, with Congress adjourning, the bill stopped. It will be reintroduced in January. By then, hundreds more war-fleeing Salvadorans will have passed through Elder's operation. They will be part of an estimated population of 500,000 refugees displaced by the out-of-control violence in El Salvador. According to the Agency for International Development, 20 percent of El Salvador's people have been exiled from their homes. Another one percent have been killed.

The masked woman at the hearings was able to leave freely. A deportation swoop in the halls of Congress is not the kind of publicity the Reagan INS is looking for right now. It prefers to pick on the weak and the poor through the quieter intimidation found in the remoteness of south Texas. In a few weeks, federal prosecutors will try to prove that Jack Elder is a criminal because he gave a car ride to three undocumented aliens from Casa Romero to a nearby bus stop.

The trial will be another harassment of citizens working to give sanctuary to Central American refugees. With some 50,000 Americans of conscience involved in the sanctuary movement, the government has a need for selectivity. Not everyone can be jailed, nor every refugee deported. Last May, the Reagan administration settled for a smaller victory. It won a conviction against another Casa Romero worker. She was picked up by the U.S. Border Patrol for giving a ride to three Salvadorans who had entered the country two weeks before. A three-month suspended sentence was all the INS could celebrate.

One beneficial side effect of the trial was the exposure of the thinking of the INS. Its district director in San Antonio, after exploding that those offering sanctuary to refugees are "preaching anarchy and undermining the federal government," said that the Reagan administration denies "as many applications for asylum from Poland as we do from El Salvador."

A reporter checked. In the six months before that statement, denials were issued to 796 Poles and 5,130 Salvadorans. The American Civil Liberties Union learned that "only three percent of the Salvadoran applicants have ever been granted asylum, whereas in 1983 there was a 25 percent approval rate for all asylum claims considered by the U.S."

The government's interpretation of deportation laws rests on the confused notion that the Salvadorans are here as "economic migrants." If that were true, why weren't these mass flights occurring 10 or 20 years ago when El Salvador was as destitute as it is now and the United States was more open? Few were coming then. Poverty was an enemy that could be fought by the Salvadorans' cultural strengths of family ties and communal sharing. Why uproot to a foreign country to be poor?

The fleeing -- recent and unprecedented -- is from guns and the policies of violence forced on Salvador's people by the Reagan administration and the complicity of Congress. At the hearings, Jack Ford, the brother of Ita Ford, one of the four slain churchwomen, told of his recent visit to El Salvador: "The war against the people continues unabated. I have been to refugee camps and seen people burned with phosphorus bombs made in the United States."

The masked woman at the hearings offered her own eloquent refutation to the "economic migrant" theory: "I had to leave El Salvador after the death squads visited my home. They were looking for me because I was helping the displaced in the refugee camps . . . The money sent by the Reagan administration to the Salvadoran government is killing our people and producing more refugees."

At the coming trial of Jack Elder, this argument will be one of his defenses. For him, the safest sanctuary is the facts.