LET IT BE accepted first of all tht the congressmen who make up the so-called Greek lobby have every right to be outraged that Turkey, five years after the fact, maintains a tight grip on nearly half of the supposedly sovereign state of Cyprus. Let it be further stipulated that during that time the Turks have done precious little to earn the good faith - on that issue - of the many Americans who are no less sympathetic to the plight of dismembered Cyprus than the Greek lobby.

But something else must be said, too. The Greek lobby is not only devoted; it is unbalanced. It has taken good cause and torn it to tatters. It has a tactical sense of what might actually bring Turkey to a more reasonable position on Cyprus, choosing instead to force the issue in terms that cannot fail to rankle Turkish patriotism and pride. And it has lost a strategic sense of how Cyprus fits with other issues of American concern.

The latest case in point centers on a $50 million item in the military aid bill. The administration wants it in order to help get Turkish hardware up to at least minimal NATO standards, and in order to sweeten the politically powerful Turkish military for the compromises - including compromises on Cyprus - the United States would like Ankara to consider. The Senate made the $50 million a grant. The House, out of the Greek lobby's spite, made it a loan. Upon learning of the calculated slight, the Turkish military put a hold on letting American U2s overfly Turkey to help monitor Soviet missile tests. Such monitoring is important, politically if not militarily, to help the administration sell the Senate SALT. Rep. Les Aspin (D-Wis.) added an unnecessary touch Sunday by stating, in an assessment of what the loss of U2 rights might mean to SALT monitoring, that the House should not "knuckle under to Turkish and administration pressure" on that account.

The integrity of Cyprus is important. But relentless economic and political deterioration in Turkey has made it impossible to keep Cyprus square in the middle of relations between Washington and Ankara. The Greek lobby's obsession is a politically unsupportable anachronism. The plain fact is that further progress on Cyprus cannot be made without restoring the health of Turkey, which is, of course, crucial on other grounds. If the Greek lobby cannot see its way clear to supporting this objective, it should at least not put obstacles in the way.