IT IS distressingly easy for anyone strolling Washington's tractor-torn Mall these days to lose all sympathy with the farmers' tractorcade and its denim-clad adherents' demands for a better life.

For the farmers of the American Agricultural Movement are confronting us not only with their machines and their rhetoric but with our own stereotyped perceptions of the agrarian way.

Throughout most of this nation's history, and particularly during the last century, the farmer has been celebrated as a swllspring of the enduring values of quiet strength and self-sufficiency and devotion to family and home.

From the poems of John Greenleaf Whittier and James Whitcomb Riley to the televised works of Earl Hamner Jr. ("The Waltons") and Laura Ingalls Wilder ("Little House on the Prairie") we have sentimentalized the farmer into some kind of noble sabage whose closeness to the soil made him somehow immune to the moral and social viruses of urban America. His, we were certain, was the simple life of the homemade biscuit and the gingham shirt -- a life innocent of such tacky corruptions as the electric can opener and the fast food fry.

Out on the Mall that image comes a cropper. Not only has the noble savage been ripping out parking meters, toppling young trees and gouging the landscape like the least responsible urban vandal, he has been whining for a short-range governmental fix to relieve his own addiction to credit card trinketry and free-spending debt. Instead of shaming us with simple phrases and humble ways, he arrived festooned with Winnebago comforts and Polaroid film. Dust Bowl rhetoric rings a little hollow inside a tractor dressed with stereo sound.

IT IS NOT comforting to have an idol fall, particularly this one. Amid the tumult of the 1970s, we need the illusion that a simpler, Norman Rockwell world survives somewhere to which we might repair, if only in the mind. We don't want farmers to be just like us. We expect more of them than that.

But if our image of the farmer requires some adjustment, and if the short-range goals of the tractorcade appear something less than noble, the larger question the farmers raise must be addressed. And that question is whether the family farm in America cam survive or whether agricultural small business must inevitably go the way of the Mom and Pop grocery.

The family farm is already a long way from 40 acres and a mule. The most frequent size claimed by the tractorcade farmers was about 600 acres, often encompassing a quarter-million dollars in machinery to make it produce. Roy M. Miller of Friona, Tex., talked of needing a $96,000 loan just to pay for seed and fertilizer on his 600 acres of grain and cotton last year.

Stanly Cairns, a 36-year-old father of five from Greanleaf, Kan., talked of losing $11,000 a year for the past three years and watching his net worth shrink from $54,700 in 1975 to $21,600 in 1977. "It used to be my dream to own every acre I farm," he said. "Then I decided to settle for just getting out of debt. Now I'll do anything I can just to keep on farming."

Cairns and Miller were two of the more soft-spoken of the tractorcade farmers, men who came to Washington to raise questions about the future. For them, there is something sacred about the continuity of generations on the land. For them, a little something of America dies whenever a family-owned farm is taken over by a corporation.

It is not simply, as the farmers like to say, that "giant corporations controlling our food can bring this nation to its knees." The big grocery chains already control our food through the stores. What is more to the point is whether a rural culture can survive, producing people as well as crops for a nation for whom farm-born diversity has traditionally been the life's blood.

For if the stereotype of the farmer is more wish than reality, and if the farmer in 1979 is prey to the same temptations to greed and instant gratification as the rest of us, there is nevertheless bred on the farm a respect for long-range values and the qualities that endure. Air-conditioned tractor cabs and CB radios have not altered the basic decency of the American farmer, however much the tractorcade may could the issue.A farmer's life, as Hobbes once siad, may indeed be "nasty, brutish and short," but a farm is still a place where children learn naturally about birth and death, and work and sacrifice, and achievement and self-respect. And even if, as is often the case, the children leave the farm; even if they hate the drudgery of farm life, they carry those larger values with them into urban America, where they're needed now as never before.

A few years ago I encountered a man in Fairfax County who had left an office job to pursue a lifelong dream of farming. He wasn't making any money, and he was sometimes bitter about the sacrifices it demanded, but he wouldn't have left the farm and he told me why.

"When I first got out here," he said, "I saw all these old farmers sitting around talking about a heavy winter coming because the caterpillars were woolly, and I said to myself, 'If these old crackers can make a living, I'm going to get rich.'

"I read every book I could on agriculture. I put down fertilizer like they'd never seen before and the first year I had the most beautiful corn corp you ever saw. And the old guys came over and said, 'Well, we know this land and it's good for cattle but it'll never hold up under row corps.'

"I couldn't believe it. Here was the greatest corn crop anybody ever saw, and they were acting like it wasn't there. So the next year I put in more corn and again it was great. The soil was testing better and I was starting to get my head above water financially. The third year I did the same, and still the old boys talked about my land not holding up under row crops. I just figured they were crazy.

"Then we had five years of drought. The first year I lost $40,000 on my corn. The next year I lost $50,000. The third year I reduced the crop and only lost $20,000. And, let me tell you, I was up against the wall.

"And all of a sudden, I saw what the old guys were talking about. They weren't saying I couldn't have a couple of good years with corn. They were talking about the long haul -- what works year in, year out, over the long cycle of the seasons. They were talking about the averages, what you could depend on.

"And now, let me tell you, I'm just like them. When I see the bees bunching up in thr trees, I hurry to get the hay in, because I know that most of the time that means a strom is on the way. I think in terms of the long haul. And I think of the long haul in terms of politics and social programs now and price fluctuations and the things I really need. It has affected the way I think about everything. I believe most in what's been tested by history. And I'll never think any other way again."