BOSTON, DEC. 17 -- The trial of political extremist Lyndon H. LaRouche Jr. and six of his longtime followers opened here today with defense attorneys saying that their clients may at times have been offensive and lacked judgment, but that they deserve their constitutional rights to free expression and a fair trial.

The defendants allegedly tried to obstruct a criminal investigation into the Leesburg-based LaRouche group's multimillion-dollar fund-raising activities for his 1984 presidential campaign. Each of the seven could receive up to five years in jail and a $250,000 fine if convicted.

"A lot of these people are among the most annoying, aggravating people you've ever met in your life," said Michael Reilly, attorney for one of the five LaRouche-related corporations also on trial, having been charged variously with obstruction and credit card fraud. "They believe that the way to make their point is to make it in the most confrontational way."

In his opening arguments for the prosecution today, Assistant U.S. Attorney John Markham described the case as a road map of the inner workings of the often bizarre LaRouche group. The trial is expected to last six months and have more than 150 witnesses, including numerous group dropouts or "defectors," and many current members.

In the crowded courtroom guarded by federal security officers, defense attorneys laid out their own case in opening statements, describing the LaRouche followers as passionate, and occasionally obnoxious, political activists who deserve the right to free expression. The six have been followers of LaRouche for 20 years, accompanying him philosophically on a path that crossed the political landscape from revolutionary socialism to the far right and then to a current peculiar blend of both.

Markham said the group's alleged bilking of millions of dollars from the public and later attempts to stifle a federal probe into the group's fund-raising tactics stemmed from LaRouche's arrogance and his followers' blind devotion to him.

"On many occasions, Mr. LaRouche has told followers that other people in our society don't deserve their money because they're slime, muck, dirt; that he alone has the intelligence to save the Western World, and that deserves other people's money," Markham said. "He said he's the boss, the commander in chief."

LaRouche and his top aides berated the group's rank-and-file fund-raisers, often challenging their sexuality if they didn't raise enough money, Markham said. After the FBI started investigating in 1984, LaRouche and his top aides conspired to send key witnesses to Europe, to hide subpoenaed documents and burn others, the prosecutor said.

Three of 12 defense attorneys made opening statements today and presented a completely different characterization of the group. They spoke of an organization devoted to all-American principles, in favor of a strong military and against drugs and communism. The defense also tried to prepare the 12 jurors and four alternates for the prosecution's harsh portrayal of their clients.

"They believe passionately, with all their energy, and with a commitment that involves their entire life style," said Attorney Matthew Feinberg, representing two of the other Larouche companies. "No matter how offensive, alien, or lacking in judgment" they may be, he said, "words are not a crime."

Feinberg said the jurors should not trust the group defectors who will testify as prosecution witnesses against their ex-leader for the first time. He asked that the jurors keep an open mind in the "hard to understand" case.

Feinberg finally warned them against believing the testimony of "exploiters" of the group, an apparent reference to two former paid group consultants expected to testify.

Both are former Ku Klux Klan activists from Reading, Pa. One, Forrest Lee Fick, has turned government informer, while the other, Roy Frankhouser, was convicted last week on obstruction charges. The government had sought to have Frankhouser's case severed and tried first so it could compel his testimony in the case by granting him immunity.

The LaRouche defendants' case rests on Frankhouser and Fick, in a defense scenario that even LaRouche group attorney Reilly calls "weird."

During many years, testimony showed, the two collected fees from the group by falsely claiming that they had a close friend who was a former top CIA official. Testimony has shown that the two persuaded a ship worker friend to pose as this so-called CIA official, code named "Mr. Ed," in meetings with LaRouche aides.

Despite the unlikelihood of the situation, the LaRouche group believed completely that those two Klan activists had an inside line through "Mr. Ed" to the White House and the Kremlin, according to defense lawyers. Even now, their defense is that it was Fick and Frankhouser who told the group to hide the witnesses and documents. The defendants added that they thought they had CIA approval in slowing the FBI probe.

Attorney William Cummings, representing LaRouche aide Michelle Steinberg, said that LaRouche followers believed -- based on what they thought were the two men's close relations with the CIA -- that the government considered the LaRouche group as "a national resource in security matters" with an immunity from prosecution.

"At all times, they were acting with a proper motive," he said.

Frankhouser faces sentencing in February on his obstruction conviction. Like the defendants in the trial that began today, he could receive up to five years in jail and a $250,000 fine.

Lawyers on both sides say some of the most dramatic testimony will come from dozens of people appearing for the prosecution, who said they were bilked by the group. They said group fund-raisers obtained large amounts of money, sometimes up to $100,000, from their credit card accounts without authorization, and then refused to give the money back.