Responsible public debate has been seriously disserved by the mindless and by now routine assertion that the closing of the Palestine Liberation Organization offices in this country would somehow restrict freedom of speech of U.S. citizens or residents.

It is legitimate to oppose the closing of the Washington office on foreign policy grounds or of the New York office because it might abrogate an international agreement. Reasonable men may debate the matter. But it is not legitimate to try to make this position palatable by falsely masking it as a First Amendment concern. Yet a Feb. 8 editorial insisted that the effort to close the New York office be defeated because it makes "the United States appear to be afraid of speech -- not terrorism, but speech." Nonsense.

The fact is that no genuine issue of freedom of speech is raised either by the State Department directive to close the Washington office or by the recently enacted legislation mandating the closing of the New York office. With the closing of these offices, Americans remain free, exactly as before, to advocate the Palestinian cause, to criticize Israel, to join the PLO or to take any other position on the Middle East they may wish, without penalty or impediment.

Hassan Abdul Rahman, director of the Washington office, remains free, as a U.S. citizen, to assert and promote the views of the PLO, exactly as before. And the PLO itself remains free to have its views and materials brought into this country and distributed without hindrance, exactly as before.

We suggest that the PLO and its advocates are less concerned that the message of the PLO will not be received in this country than that another message will be sent throughout the world -- namely, that the United States regards the PLO as an instrument of international terrorism whose presence is not welcome in decent society.

The State Department closed the Libyan Embassy with no claim from anyone that freedoms of American citizens were thereby infringed. And it is doubtful that First Amendment considerations would be heard from critics of the PLO office closings if we closed the South African Embassy because of our revulsion against apartheid.

The order to close the PLO office in our nation's capital has already demonstrated our country's resolve to go beyond mere preachment and rhetoric in its fight against terrorism. This constructive message will not be lost on the other nations of the world.

PHILIP BAUM Associate Executive Director, American Jewish Congress New York