OFFHAND, WE CAN THINK of no more representative and respectable spokesman for the opposition to the new Panama Canal treaties than Sen. Barry Goldwater of Arizona. And so we listened carefully as he explained after a White House briefing on the treaties the other day why he is confident that the American people won't be willing to give up the Panama Canal. "Don't ask me why," the senator declared. "It's like the American flag - they're wrapped up in it." Don't ask me why. In other words, what the senator would apparently have us belive is that the American public has got the Panama canal issue so interwined with the flag and love of country and all the rest that to argue the case in reasoned and realistic terms is a waste of time - so don't argue.

Well, we don't believe that to be the case. But we don't doubt that Sen. Goldwater believes it. Nor do we doubt, having heard much of the formal argument in opposition to the treaties, that the mindset described by the senator applies to a large number of the treaties' loudest opponents, and to a significant slice of American public opinion as well. Indeed, it is precisely the "wrapped up" quality of the case against the treaties that makes today's encounter between Presidnet Carter and Panama's visiting Gen. Omar Torrijos both a useful opportunity to clarify some overblown confusion about some of the treaties' terms - and an exercise in futility.

The President was careful at his press conference yesterday to leave open the question of whether he and the general will decide to issue a joint statement on the two most sensitive issues that have been raised about its terms: the rights of the United States to do whatever is necessary to keep the canal open and "neutral," and the right of "expeditious passage" for American warships. It could well be that Gen. Torrijos, facing a referendum on the treaties in his own country on Oct. 23, may wish to defer further public comment at least until his return to Panama. But the meeting, at the very least, offers an opportunity for both men to demonstrate that the varying interpretatins of the treaties' terms in this country and in Panama are rooted in practical politics - and are reconcilable. By way of illustration, we would cite the way Mr. Carter handled the delicate "intervention" question yesterday. "We are determined," he said, "that the canal will be open, neutral, and free for use as long as it is there beyond the end of this century." But once having thus plainly proclaimed this country's right under the treaties to do whatever it thinks necessary to keep the canal open, the President made clear his awareness of the sensitivity of Panamanians and most Latin Americans to the suggestion of "Yanqui imperialism" that is implicit in the codeword "intervene" by adding:

"We don not have any inclination to intervene in the internal affairs of Panama. When we say in this country we reserve the right to take action to keep the canal open, when they say in their country we do not intend to permit the United States to intervene in the internal affairs of Panama, we are both right."

Now that seems reasonable to us. Both it is also probably true that nothing that Mr. Carter and Gen. Torrijos could say today on that score (or on any other aspect of the treaties) would seem reasonable to those who oppose the treaties - and don't want to be asked why. It is only to that extent that today's meeting between the two men can be considered an exercise in futility - only to the extent, that is to say, that Sen. Goldwater is right about the "wrapped up" state of mind of most Americans on the Panama Canal. If President Carter can develop the case for the treaties as effectively as he discussed it at his news conference yesterday, we have a lot more confidence than Mr. Goldwater apparently has that a lot of Americans and a good number of U.S. senators who now may be in doubt will be willing to listne to a reasonable argument.