More than a dozen conservative organizations last night honored Roberto D'Aubuisson, the leader of El Salvador's extreme right wing, with a plaque and a closed-door dinner for 120 people at the Capitol Hill Club.

The plaque expresses appreciation for D'Aubuisson's "continuing efforts for freedom in the face of communist aggression which is an inspiration to freedom-loving people everywhere."

D'Aubuisson also has scheduled a speech tonight at Georgetown University, and some students are organizing a protest.

A former Salvadoran army major who was cashiered for plotting coups, D'Aubuisson has been linked to death-squad murders in El Salvador by former U.S. ambassador Robert E. White and congressional testimony. But D'Aubuisson and the conservatives insist that the charges are false and spread by Marxists opposed to his democratic, free-enterprise views and to the conservative ARENA party whose unsuccessful presidential candidate he was.

Richard Mathias, a Georgetown student and official of the Young Americans for Freedom, said the YAF had arranged D'Aubuisson's campus appearance because D'Aubuisson "hasn't had a fair shake" in the U.S. media.

"Death squads have a very negative connotation. He's not been able to get across his message of free enterprise, anticommunism, freedom of exports and imports," Mathias said. "We can't think coherently about El Salvador if we think of the primary antithesis to the government as being a death-squad leader."

In a meeting with Washington Post editors and reporters yesterday, D'Aubuisson said lack of progress after two rounds of talks between the Salvadoran government and leftist rebels had strengthened him because it proved he was right in holding that dialogue with Marxists "cannot achieve anything."

"I don't see where we can continue talking," he said. He noted that Salvadoran President Jose Napoleon Duarte had used D'Aubuisson's own words in calling the rebels' position intransigent. Duarte, D'Aubuisson said, had agreed to the talks "to improve the international image of the country . . . and to get more votes" at home.

"What I criticize is that he Duarte is playing with the hopes of the Salvadoran people to reach peace with this demagoguery," D'Aubuisson said. He called on Duarte to talk more with conservatives, farmers and businessmen -- many of whom support D'Aubuisson -- as well as with the rebels, and predicted that conservative opposition forces would retain control of the Salvadoran legislature after elections in March.

Asked whether he favored aiding the United States in its opposition to the leftist government in neighboring Nicaragua, D'Aubuisson said that involving Salvadoran troops in any action against Nicaragua would be "the worst thing that could happen" in the region.

Rebels resisting Nicaragua's Sandinista government "enjoy our sympathy . . . , but that is an internal problem," he said. Marxist literature talks of "Vietnamizing" the fighting, which means internationalizing it, he said, and "in the long run, the Soviets win in that way."

Groups that joined in presenting the plaque to D'Aubuisson included the Viguerie Co., Gun Owners of America, the Western Goals Endowment Fund, the Washington Legal Foundation, the United States Defense Committee, the American Foreign Policy Council, the Public Service Research Council, the Moral Majority, The Washington Times, the National Right-to-Work Committee, the National Pro-Life Political Action Committee, Intercessors for America, the Young Americans Foundation and the Young Americans for Freedom. Presidential assistant and former U.S. ambassador Faith Ryan Whittlesey also joined in the presentation, but reportedly did not attend the dinner.

Groups that joined in presenting the plaque to D'Aubuisson included the Viguerie Co., Gun Owners of America, the Western Goals Endowment Fund, the Washington Legal Foundation, the United States Defense Committee, the American Foreign Policy Council, the Public Service Research Council, the Moral Majority, The Washington Times, the National Right-to-Work Committee, the National Pro-Life Political Action Committee, Intercessors for America, the Young Americans Foundation and the Young Americans for Freedom. Presidential assistant and former U.S. ambassador Faith Ryan Whittlesey also joined in the presentation, but reportedly did not attend the dinner.

Other hosts for the dinner included the Free Congress Foundation, the Conservative Caucus and the Conservative Alliance, according to Lynn Stoner of the National Council for Better Education, who helped organize the event.

Stoner said Sen. Jesse Helms (R-N.C.) had been invited but was unable to attend.

D'Aubuisson causes a debate within the State Department each time he applies for a visa. He was denied entry in November 1983 in what U.S. officials said was an effort to avoid taking sides in the Salvadoran elections last March that D'Aubuisson lost to Duarte. D'Aubuisson visited Washington for three days last June.