If you ever wondered why Washingtonians feel so hermetically sealed off from the rest of the country, take a look at "The Battle of Westlands" tonight at 10 on Channel 26.

The hour-long documentary, crafted with skill and grace by two independent filmmakers; Sandra Nichols and Carol Mon Pere, tells the story of the 600,000-acre California valley irrigation project, battleground for a classic confrontation of agribusiness and small farmers.

It aired in the rest of America over a month ago. But Washington's PBS station WETA decided the film was too one-sided against big business and so added a postscript show of its own.

The reason, WETA executives said, was not only that they thought the film biased but that legislation was pending on the Hill and the station didn't want to be accused of lobbying.

A reasonable point. The fact is, however, that the WETA-staged debate by four talking heads -- two for, two against -- turns into a shouting match. In the end it manages to obfuscate the issues into an incomprehensible jumble of advocate views.

It is complicated enough to begin with. Under the Reclamation Act of 1902 the land was turned from virtual desert into the world's richest farm bottoms by a $5-billion irrigation project. U.S. taxpayers paid for it, and the object was to make the land arable and to encourage settlers.

But instead of honoring its own 160 acre limit, the government let large concerns, a mere 200 of them, take most of the land. Tenneco, Standard Oil and the Southern Pacific Railway are among the owners.

Nichols and Mon Pere have laid out the past and present situation in a way that seemed balanced and fair from here, anyway, given the hard requirements of an hour-long TV show. It was typical serious television, with opposing sides arguing each issue in turn.

For millions of Americans, this is the way the controversies of our day are presented: the beautiful visuals, the outlines of conflict, and finally the hard-going detail stuff after our interest has been thouroughly engaged.

Only in Washington would it be felt necessary to translate it all back into abstractions, adding a lot of heat but very little light. WETA's concern for the overdog is touching.