Geraldo Rivera has unsheathed his sword again, and unsheathed his thesaurus as well. The ABC News correspondent, grand wazir of the gonzos, goes a-flailing on a special segment of "20/20" tonight, exposing a virulent strain of anti-Semitic fanaticism among impoverished family farmers in the Midwest. While it is encouraging to find any television broadcast of any kind with even an ounce of passion behind it, Rivera's report comes across as journalism more agitative than investigative.

In the report, an unqualified shocker to be seen on "20/20" at 10 on Channel 7, Rivera maintains that, in their desperation for a scapegoat, some embattled farmers (how many is never made clear enough) have turned to age-old racist conspiracy fantasies being summoned up yet again by factions of the far-far-far-far right. Rivera seems excessively eager to make it clear where he stands; thus, the subjects of the report, titled "Seeds of Hate," are "racist hate groups," "preachers of hate" and "demagogues" who espouse "the philosophy of hate," reap a "harvest of hate" and wage an "unholy war" with a "malignant philosophy" that is also a "sick philosophy." We wouldn't want anyone to miss the point.

"If Hitler had a religion, this one would be perfect for him," Rivera snarls of one radical sect. "It would be comforting to think it was limited to just a handful of extremist nuts," he says of the militancy, "but it's bigger than that. There is trouble now in the heartland," he ominously rumbles. Early in the report, Rivera ticks off a series of violent incidents he links to the hate groups, and each one is hyped by the sound of gunfire on the sound track. Would anyone but Geraldo, and any news division but ABC's, resort to quite so crude a gimmick as that?

What Rivera and crew got on film is creepily disturbing, but he never convincingly builds a case for his own conspiracy theory: that the radical right is somehow uniting the dissolute and the disillusioned to form a new fascist, white-supremacist army. Rivera links such lunatic groups as Christian Identity and Aryan Nations to the desperation of farmers facing foreclosure. Their brains, it is suggested, are ripe for the washing, yet we remain uninformed of the scale on which this is occurring, and there is barely a token effort to examine the roots of the farmers' frustrations or why they may be susceptible to this strain of ideological corruption.

There has always been, and, sadly, probably always will be, a lunatic fringe, and a violent lunatic fringe, abroad in the land. Just dealing with this subject seems a tainting, demeaning experience, something to be approached with utmost caution. A reporter needs an awfully sturdy peg to justify bringing it all up on network television and thereby granting it wildly amplified circulation. At times it seems the alarmist rhetoric used by Rivera is an attempt to finesse what is really a weak case for his own sensationalism.

Just as added insurance, Rivera offers another rationalization at fade-out time: "Add stopping the ministers of hate to all the other more compassionate reasons we should be helping America's family farmers." Oh, so that's what the report was about! Geraldo just forgot to mention it until the end. 'Washingtoon'

Bob Forehead is a vacillating lint-brain, so it was inevitable he would seek a career in politics. In Mark Alan Stamaty's inspired weekly comic strip "Washingtoon," Forehead's wanderings in the Capital jungle lead him from one wellspring of opportunism to another, all in the good name of laceratingly waspish satirical comment. Most of the elements that make the strip funny and valuable have been jettisoned for standard sitcommery in the TV version of "Washingtoon" that premieres on the Showtime pay cable network at 10:30 tonight. The pilot, which aired last spring, needed work and didn't get enough of it.

Thomas Callaway, who looks like a slightly melted James Franciscus, seems entirely adequate in the role of Forehead, the hopelessly dim-willed freshman congressman. "So," he asks, addressing the House for the first time, "how many of you are from out of town?" There are moments, but Neil Cuthbert, who "developed" the strip for television, developed just about all the snap and sting right out of it. The sole highlight of the premiere is a takeoff on the "We Are the World" video called "We Are the House," and even this is so lame it would never survive the first cut at the annual Gridiron Club revue.

Barry Corbin, so memorably pithy in "WarGames," is wasted here as the heavily seasoned minority whip who tries to nudge Forehead in the wrong directions; but Beverly Archer, who has been seen in dozens of TV commercials, is amusing, in an Andrea Martin-Margaret Hamilton sort of way, as his absolutely-no-nonsense-not-even-if-your-life-depended-on-it secretary. The sitcom family invented for Forehead is embarrassingly trite, not satirically trite as may have been imagined.

Named "yuck of the week" for advocating that beer and television set expenses be made deductible, Forehead laments that "half the country is laughing at me." Even if Showtime were available to every TV viewer in the land, that statement would be a reckless overestimate.