FIDEL CASTRO has done a very vicious thing in effect, throwing out of Cuba in the most hazardous and undignified way those Cubans whom he has decided to let go if they wish to leave. The move is designed chiefly to embarrass the nations, especially the United States, that criticized him for the earlier episode at the Peruvian Embassy when 10,000 Cubans abandoned their whole life in Cuba the instant it became possible to depart. The move is also intended to purge Cuba of elements economically and politically burdensome to it -- apparently Cuba is taking the occasion to empy some of its prisons, too.

Presumably these are the considerations that made Mr. Castro decide that it was worth enduring the broad international derision that the spectacle of mass voluntary flight from Cuba has elicited. Indeed, this spectacle shreds any lingering claim the regime may have had to being considered a marvel of socialist development worthy of praise or emulation by others. The example and tales of those now fleeing confirm that communist Cuba is, except for the favored few, a slum and a prison to boot.

At the same time it is plain that the proximity of Cuba, the appeals and actions of the many former Cubans already living in this country, and the fresh tinge of anti-communist feeling in the air make Mr. Castro's cynicism much more than a matter of propaganda for the United States. The Cubans are streaming out of Cuba in small boats, chancing tropical storms that have already cost a number of lives, often ignoring the customary procedures for people seeking asylum and straining the resources and facilities available to welcome them. All of this can be attributed to the pressures of an emergency, but the response of the U.S. government is something else. Distracted, it has taken the position that the Cubans are not respecting the proper legal procedures and that economic distress makes this the wrong time for a large number of unscheduled immigrants to come in.

The official position is not without some logic. There is, after all, a new law under which the government is supposed to regulate the flow. There is a recession. It is inconsistent for the government to admit Cuban boat people even while it is fighting in court to deport Haitian boat people. The Haitians are more typical of the immense numbers of people throughout Latin America and the Caribbean who ache to immigrate to the United States but, unlike the Cubans, cannot mobilize a constituency to help them get in.

But the important overriding point is this: the Cuban situation is special. By announcing they wish to leave Cuba, these people have cut their ties. They are in the boats of the "freedom flotilla." They are surging into Florida. To most Americans it is unthinkable to put difficulties in their way. It is not just an open door allows the United States to make a propaganda point against Fidel Castro and to defeat his effort to show that the United States talks big about liberty but is too selfish to help people in trouble. It is that, in offering refuge to people fleeing tyranny, the United States is being true to what it most deeply believes.