Late one rainy afternoon last week, coming back to the office from Capitol Hill, I boarded the Metro and took a seat by the door. Seconds later, amid the crush of rush-hour travelers catching the train, a slim, young, blond man pushed his way through the throng and sat down in a seat opposite, facing the door.

He was carrying an umbrella and some books and was dressed in sneakers, black trousers and a light, gray type of athletic warmup jacket that zipped up the front. Across the front of the jacket, covering the width of his chest, printed in bold black capital letters, were the words: THE JEWS KILLED CHRIST

Down the right side of his face, from the corner of his eye to his jaw, ran a straight line of bright red blood. It looked as though it came from a fresh cut by a sharp knife. Of course, it could have been stage makeup, but the appearance was all too realistic.

What became fascinating about this sight was not the young man but the reaction of his fellow passengers. While I was aboard, the train stopped five times to discharge and pick up passengers. Not once did a single person give him the satisfaction of the attention he so obviously craved. Each quickly took in this appallingly sick scene and acted as though he didn't exist. If even a flicker of emotion crossed their respective faces, I didn't catch it, and I was watching intently. At the stop before I detrained, a man wearing a camel's hair coat boarded, took the seat beside me and softly remarked, in a half-rueful, half-sad sort of way, "God, that's spectacular. The only thing you can say about that is: Only in America could anyone get away with that."

He shook his head slightly and continued to look straight ahead as if determined to deny the young man any response to his shocking behavior.

I left feeling strangely impressed by the collective reaction of fellow passengers. In a most unpleasant situation, all had been calm, cool and studiedly impassive. In the face of an extremely provocative encounter, they had shown instinctive wisdom in letting a sick fool remain in isolation and, despite a clear attempt to incite them to emotional response, had borne the incident well. It was an affirmation, I found myself thinking, of the basic good sense of my fellow citizens.

Perhaps that incident deserves no more than a passing notice, and certainly it's perilous at best to draw from that limited specific scene a more general observation about Americans today. But foolish or not, I will attempt to do so here.

Economic developments of recent months have underscored a paradox about the country. Despite increasingly difficult and in many cases desperate times for millions of people, there has been remarkably little display of public emotion over worsening conditions. Various interpretations have been given for this.

Some have suggested this is so, in part, because the people still have faith in the president; they believe his policies will prove correct in the end. Others have testified to the basic sense of optimism that pervades Americans, both past and present, a view to which I subscribe.

I have also heard it argued, as in a personal exchange with a wealthy Wall Street investment broker immediately after last fall's congressional elections, that the absence of anger should not be surprising: people aren't really hurting, he said, and they have plenty of benefits to sustain them anyway, an outrageously false view that still rankles whenever I think of it.

President Reagan offered another opinion at his news conference Wednesday night. He was responding to a question about the belief of Miami officials that recent rioting there was caused as much by joblessness and economic hardships as by racial tensions. Did he think there was a danger that with people's backs against the wall during this recession they might vent their frustration in acts of violence?

The president disagreed and then gave a history lesson from the Great Depression: "It certainly would bespeak a difference in the character of our people because in the Great Depression nothing like that ever took place when the situation was much worse and there was no unemployment insurance and . . . for a time not even any welfare programs of any kind to help out."

I think the president was correct when he castigated the self-fulfilling doom talk of Miami officials by saying: "When responsible leaders, supposedly, voice their opinion that this violence is going to happen they are encouraging it, and I think they ought to think again before they open their mouths."

But his Great Depression analogy was false. He obviously has forgotten that farmers in his native Midwest sabotaged milk deliveries and food shipments and stood by with shotguns to keep their homes from being foreclosed, or about the violence that stained the nation's capital when Army troops brutally dispersed the sad World War I veterans marching for a bonus in the worst of the Depression days.

My own sense is that we are witnessing two sides of the American character that have long been with us: an inherent resiliency and native hope that keeps bubbling up in times of real adversity, but also a deepening level of concern that often breaks out in acts of desperate rage, and I am not talking about racial disturbances as in Miami.

Just a day before the president's news conference, for instance, the papers reported how farmers in Springfield, Colo., were dispersed by tear gas after they stormed the steps of the courthouse shouting, "No sale, no sale," in an attempt to block a public farm auction. And I can testify, as only one small example, to a marked change in the nature of mail I receive from readers around the country. More and more people are expressing new anger over conditions in what I take to be clear signs of growing economic class resentments and increasing political disenchantment directed at Congress and president alike.

A man from Titusville, Fla., prompted by scenes of this recession to recall old Depression memories and new evidences of anger, writes, in a barely legible hand:

"I use to see my father go to the Paper Mill hiring office 3 time a day 7:30 am 3:30 pm & 11:30 pm for work, he pick up 1 day a week sometime 2. The work he did it was to degrading but we survive . . . .

"Another thing that must make them unemployed very mad is when you watch on TV the Rose Bowl parade. Why don't they cancel that one year & help these people out. The cost of them floats must cost thousands. This country is not on the bum by any means but it may get there if Congress dont stop helping themselves & do whats good for the country instead of thier pocket. I see they got a raise, but really how many need it. They certainly dont lead by thier example. Excuse the writing, I didnt get to much schooling."

The moral seems to be as old as it is familiar: even for long-suffering and optimistic Americans, patience has its limits. And, prudent behavior on a subway train notwithstanding, we could be approaching them.