This is a time for those who value conciliation and realism in international affairs to be supporting the new Panama Canal treaty. But it is also a time for those who prize integrity in human affairs to offer respect to Leopoldo Aragon, the Panamanian who set himself afire outside the American Embassy in Stockholm on Sept. 1 and died of his burns the next day.

Born well in Panama, he studied at Santa Clara and UCLA and in Europe and took up a career as an international journalist; I met him in Washington in the 1960s. A democrat (and Social Democrat), he had an ironic and intellectual cast of mind and nourished Simon Bolivar's vision of a united Spanish American devoted to social justice. Of the left? Yes. A Communist? Czechoslovakia expelled him in 1967. His widow insists he never belonged to any Communist-affiliated organization; the State Department, in denying him entry last month, contended otherwise.

Returning home in 1971, Aragon opened lines to strongman Omar Torrijos but soon soured on him. As he wrote last month, he was then "condemned, without trial, by executive order in Panama to five years in a Coiba Island concentration camp, under the mere suspicion that I had read the Corps of Engineers Draft Position Paper."

That "paper" of Feb. 16, 1968, Aragon wrote, started with the fact that popular opposition had washed out the new treaty the civilian government of Panama had negotiated with Lyndon Johnson in 1967, and concluded that the United States could get a new treaty only by encouraging and supporting strong military rule. The man identified in the "paper" as the likeliest person to do the job was Torrijos, who led a coup the following October.

Was there actually such a "paper" or plan or guideline drawn up by some part of the U.S. government working through the engineers? The CIA, when questioned, professed to know nothing about it.

After 15 months' imprisonment, Leopoldo Aragon was exiled to Sweden. Rose Marie Aragon, an American citizen, says, "He had broken bones, his kidneys were a mess and he was suffering from a terrible bronchitis.

The canal talks were moving and Aragon set up the "Liberation Command of Panama," apparently little more than a one-man letterhead. By phone, pen and personal agitation he protested that Panama was yielding too much. He demandded that a treaty he approved not simply in a government-controlled up-or-down referendum, as Torrijos now plans, but in a genuinely free plebiscite in competition with other canal proposals.

Last July he applied for a visa to carry his case to Washington (and to put his 18-year-old twin daughters in college). He was refused, he was told, under Section 212 (a)(28) of the Immigration Act, a catchall article barring anarchists, Communists and the like. No supporting detail was given him or, when I asked, me. I was also told, again without supporting detail, that he was refused as well under 212 (a)(1 27), the article barring people "prejudicial to the public interest." He wrote me: "The baddies don't let you out, the good ones don't let you in, 'by law.'"

Was he excluded by a reflexive bureaucratic distaste for leftists, perhaps enhanced in his case by a wish to sweeten the atmosphere at Panama treaty time? Yesterday, in a second response, the State Department informed me, without elaborating, that "he had been connected with Communist intelligence services" and "there were indications he would cause disturbances." Nonetheless, apparently in part as a result of visa-easing legislation signed into law on Aug. 17, his application was being reviewed when he died.

Mrs. Aragon had come to Washington on Aug. 14, having been assured by her husband that he contemplated nothing untoward. He told the girls, who left for New York on Aug. 27, that on treaty-signing day he would chain himself to the Stockholm embassy gates. But on Sept. 1 he set himself afire. On Sept. 2, the day he died, Mrs. Aragon received a letter that he had given their twins to mail from New York.

The letter said: "I know what I have to do to be faithful to my destiny. I feel it with all the depth of conviction that a man can have. No more words. I love . . . the Panamanian people. I want them to become Columbine (devoted to latin unity). And I am going to do something that can be instinctively understood and appreciated."

There is a movement on among liberals in Washington to hold the new treaty morally if not politically hostage to the cause of human rights in panama. The movement is being supported, not too discreetly, by conservatives and treaty foes for their own reasons. I think it is misguided. There are legitimate reasons of high policy to play down, at least for the time being, whatever may have been the Torrijos government's past excesses: The treaty is too important. Aragon was an idealist and intellectual whose treaty views, if accepted, would likely have produced great crisis in Panama and in hemispheric relations. But he was also a valorous man who posed the gravest threat, it turned out, to himself.