President Reagan might be surprised to learn that ideology does not much figure in what Maria says. She left Guatemala some time ago but keeps in touch with her old village. As a result, she can provide the names and the ages of those killed, but there are some things she does not know. She cannot tell you, for instance, who killed them or, for that matter, why. She knows only that her former neighbors are dead.

Roberto was decapitated. Men in uniform came to the prayer room in the church where he slept and took him away. It is not known if he was killed by soldiers or by guerrillas wearing army uniforms. All that is known is that Roberto was decapitated.

Felipe, 23, married and with two children, disappeared.

Juan, 45, was roused from his sleep at night and has not been seen since. He was married and the father of three. The military said he was a guerrilla, although they do not say that they killed him.

Ernesto, 20, went to the market and never came back.

Gabriel, 25, married and the father of three children, was taken from his house at night. He was held for two weeks by the military before friends managed to free him. Too late. By then, he had been blinded.

President Reagan said the other day that if we lose in El Salvador and then maybe in Honduras, America will be inundated with refugees fleeing communist tyranny. Maybe he is right. But what he did not say is that the refugees are already here, some of them running from just the sort of terror the president thinks will follow a leftist victory in Central America.

In the heart of any big city you can find Salvadorans or Guatemalans who have fled the terror and, of course, others who have fled poverty, and others who have fled both. In Washington, there are so many immigrants from tiny Salvador that 10 percent of the local Hotel and Restaurant Employes Union is from that country and the Adams Morgan section of town is now Little Central America. Unless they are sadly deceived people, they did not come to Washington for the weather.

The threat of a wave of immigration has always been a reason--although a largely unspoken one--for opposing the establishment of leftist regimes in Central America. Especially in the Southwest, where illegal immigration is already a considerable problem, the word has been going around that the only thing that stands between us and a tidal wave of refugees from Central America is the continued existence of friendly regimes there. Should they collapse, so the argument goes, there would be an exodus of even greater dimensions than that from Vietnam--"foot people and not boat people," as the president put it.

Even if you give the president the benefit of the doubt and excuse what amounts to pandering to xenophobia, there are still two things wrong with what he said. The first is that it presupposes that all leftist regimes, even Marxist ones, are alike--that what happened in Vietnam will happen in, say, El Salvador. This overlooks the differences between the two countries--ethnic as well as ideological--and conveniently ignores the fact that there has been no great exodus from Nicaragua.

The second reason is none other than Maria herself. She left Guatemala simply because things there were rotten for her. That's why other members of her family came here, why they live now in crowded apartments and work for less than the minimum wage at jobs they would not touch back home. It hardly matters to them what the government calls itself--Marxist, democratic--or whether it is friendly to the U.S. What matters is the life they live--in some cases, whether they live at all.

History teaches that a Marxist regime is likely to be undemocratic, sometimes brutal, often totalitarian. But then that is a fair description of the Somoza regime that preceded the Sandinistas in Nicaragua and from the standpoint of the Indians, it comes close to describing the regime of Gen. Rios Montt in Guatemala.

Once again, the president has introduced ideology where it does not belong. As Maria can tell you, it does not matter what the man who is beating you believes. What matters is that he is beating you.