Really, Mrs. Gandhi?

United States support of a far-right repressive regime in El Salvador can be debated - and is being debated in the US Congress. But who could seriously equate it with the massive Soviet invasion of Afghanistan? Prime Minister Indira Gandhi could - and did on nationwide television during her visit to persuade Americans that India's nonalignment lives, despite what you may have heard about its Moscow connection.

The trip and an increased spirit of good will between the world's two largest democracies are welcome. But it was a parody of nonalignment to say that the US involvement in El Salvador (50 military advisers plus arms and economic aid) may not be ''exactly'' the same as the Soviet subjugation of Afghanistan (100,000 invaders). Mrs. Gandhi said that the Soviets were invited by the Afghan government after rebels received outside help - as if this were no different from the way Washington is responding to requests from the Salvadoran rulers faced with rebels getting outside help.

The trouble is that such differences are blurred to many in the ''nonaligned'' movement. The prime minister does no service to truth or justice by proclaiming from her eminence that it makes no sense to draw distinctions.