THE PRESIDENT makes a grave mistake, in our opinion, when he succumbs to a temptation to make vaguely misleading debating points in behalf of the coming SALT II treaty. We understand that the temptation must be great, not to mention the provocation. Did we not detect just the tiniest hint of a retaliatory sideways clop at Henry Kissinger, architect of SALT I and recent agonizer over the wisdom of SALT II, in the president's observation in Atlanta on Tuesday that the new treaty would "reverse the Soviet numerical advantage temporarily established in the SALT I treaty of 1972"? Never mind. That wasn't the worst of it. The worst of it came in what directly followed:

To reach these [SALT II] levels, the Soviet Union will be required to reduce their overall number of strategic arms. Over 250 Soviet missiles or bombers -- 10 percent of their strategic forces -- will have to be destroyed or dismantled .

Now, there is something very positive and reassuring about the idea of the Soviet Union's having to destroy or dismantle a tenth of its strategic forces under the terms of the SALT accord Mr. Carter is negotiating. But the real-life implications of what is going to occur do not match those that the president's audience probably imagined. To come down from its present force of around 2,500 strategic launchers to the prescribed 2,250 of SALT II, the Soviets will be obliged to get rid of over 250 missiles and bombers all right; but these are certain to be among its obsolete and obsolescent stock, and it will be free (and likely) to more than make up for any prospective loss to its arsenal by adding permitted additional bombs to the launchers the treaty allows. The point is that at the end of all this the Soviet strategic force may technically and by one measure be down by 10 percent. But it will almost certainly also be stronger by several thousand additional deliverable nuclear warheads.

We are strongly disposed to support a sound and workable SALT II treaty and fairly confident that the president will bring such a treaty home. And it is for precisely that reason that we find Mr. Carter's Atlanta foray into hocus-pocus on the subject so disturbing. These clever and readily demolished arguments will end up doing the prospects for approval of SALT II more harm than good. The people who are not disposed to support a treaty -- sound and workable or not -- will not need 40 seconds to see what is wrong with them. And if the president is seen by the public to be playing debating games on the subject, then, in our view, all will shortly be lost.

The fact is that a case can be made -- a serious, plausible case -- for the value of the treaty condition the president was making so much of. There is something useful and beneficial in getting both sides to accept the discipline of limits on strategic nuclear weapons that require the destruction and dismantling of any part of either country's nuclear force. It does not add up to anywhere near so impressive and consoling an achievement as Mr. Carter's speech would suggest. But it does constitute an important step toward bringing those lethal arsenals under control and toward each country's accepting the idea of negotiated, verifiable limits. That is what the president should be explaining. His case is better than what you would believe from that little bit of flummery in Atlanta.