IT'S A DISGRACE that for 40 years the UNited States has supported the military instrument, the National Guard, by which the Somoza family has ruled Nicaragua as its personal turf. But thanks to the life that the Carter administration has breathed into the human-rights cause, there's now a good chance to cut the Nicaraguan item was rejected 22 to 21 in the Appropriations Committee last week. An effort will be made today on the House floor to put it back into the $7 billion military-aid bill. It's only a few nickels, but the effort should be voted down.

House members might consider that because of the Nicaraguan government's repressions, the State Department hasn't yet turned over last year's appropriation. It made a likewarm formal request for a new appropriation but did not push it in the face of the opposition mobilized by Rep. Edward Koch (D-N.Y.). The loss to the prestige of the Somoza family, if military aid for Nicaragua were ended, would doubtless be severe. Indeed, that's the point. But what would be the loss to American security? Asked that question, Assistant Secretary of State Lucy Benson replied, "I cannot think of a single thing."

Traditionally, many moderates and conservatives in Congress have hesitated to act on human-rights allegations on grounds that the sources of such allegations tends to be "leftists." Here, however, the strongest cast against the regime has been made by Nicaragua's united Catholic bishops, members of the establishment, who in a January pastoral letter denounced their government's "arbitray detension, torture, rape and executions without previous trial." Note, too, that the government's friends had the opportunity, in the House hearings, to reply. Even witnesses summoned by Rep. John Murphy (D-H.Y.), an old classmate of Gen. Somoza, could find no political bias in the bishops' statement.

Why, some will ask, dump on little Nicaragua, which has so often gone our of its way to accommodate the United States? The answer is that by accepting at the Somoza family's small favors, the United States has made possible its large abuses. Fortunately, Nicaragua is not, say, South Korea, where security considerations complicate human-rights confactor of American security requires the United States to persist in military support of a regime that, we believe, scarcely a single American would willingly accept for himself.