THE SOVIET GOVERNMENT has now given a 13-year sentence to Anatoly Scharansky and eight years to Alexander Ginzburg and, at a less-publicized trial in Lithuania, 15 years to Viktoras Petkus, and has brought upon itself a measure of international opprobrium virtually unprecedented in recent years, all of it richly earned. There can be few decent people anywhere who are not appalled by the Kremlin's acts of judicial vengeance against some of its worthiest citizens. That the sentences could have been more severe is hardly mitigating. Everywhere people are enraged.

Just because the Soviet performance is enraging, however, there is a special need to try to keep emotional reactions in check. That can be done, we believe, without compromising the common outrage. The Soviets made a calculated judgment that they would gain enough in internal discipline to compensate for the predictable losses in external respect. They also evidently intended to demonstrate to Jimmy Carter that he cannot intervene in behalf of Soviet human-rights figures without subjecting them to heavy personal costs. Mr. Carter's renewed expressions of protest, after the Scharansky sentencing, do not offer much confidence that he has gotten the Soviet message. We hope, when a little time has passed, that he will. Mr. Carter should understand that no one questions his devotion to the cause of human rights. He does not have to keep proving his passion. What is at issue is whether a frontal presidential assault will serve the cause he cherishes. The evidence of the trials is that it will not.

The further evidence of the Vance-Gromyko talks on SALT in Geneva, which took place even while the trials were going on, suggests that arms-control negotiations are of enough value to both governments to make them both try to insulate those talks from other aspects of their relationship. Mr. Carter has made this his stated purpose from the start, and the Kremlin seems to go along with him. We entirely agree that this is the right course. Yet this is not the end of the affair. The Russians by their indefensible and provocative internal behavior and the president by his high-pitched and self-indulgent response have fed into the American political process a tension that runs directly counter to the relative calm needed to enhance the prospects of ratifying an arms-control treaty. Here is where Mr. Carter in particular must show a great deal more caution that he has. If he thinks that, just by asserting that he separates SALT from human rights, others automatically will, too, he is fooling himself.

There are apparently hints that at least Mr. Scharansky might be exchanged for one or both of the two Soviet citizens currently under indictment for espionage in the United States. Such a swap would lend an appearance of credibility to Soviet charges that Mr. Scharansky was a CIA spy. But that political consideration is outweighed in this instance, we feel, by the moral obligation to do what is possible to gain relief for this unfortunate man. Mr. Scharansky's troubles began, after all, only when he asserted a right - to emigrate to Israel - that the Soviet government is pledged to respect. Mr. Ginzburg's offense was to take literally the Soviet Union's formal promises of civil rights to its own citizens. They are brave men, and if there remains something feasible to do to help them, it should be done.