In Waterloo, Iowa, last week, after President Reagan's speech about the twin crises on distant battle fronts, a businessman said he felt very positive about everything--with one exception: the news media.

He had been watching television that morning and frankly was disgusted, he said, to hear the news people criticizing the president for their not being allowed to cover the Grenada invasion. He thought the president was correct. What right did the news people have there anyway? They'd only make things worse.

My guess is that the Waterloo businessman was reflecting the views of an uncomfortably large number of Americans. If you took a poll today about how Americans feel about the news media, and such are taken from time to time, I'll bet you'd find the regard in which we are held to have sunk even lower in the public mind.

And that, though it may sound like special pleading coming from this second-generation member of the press, is both a tragedy and a danger for the nation, especially now.

There are many reasons to explain why people feel that way. Some reasons have obvious merit, some do not. But here, at least, is part of the indictment that this reporter hears from relative strangers when traveling the country or, more personally and pointedly, when meeting old friends one hasn't seen in years:

We are bearers of bad tidings, merchants of misery and gloom and doom. We invade people's homes, flock around tragedies, stake out homes of those in distress, interview grieving widows, ask rude, insensitive, stupid questions: How do you feel, Mrs. Jones, now that your husband has been killed? . . . . Tell us, little Melissa Sue, what you were thinking when you heard the news that your Daddy had died? What went through your mind, Harry Brown, when you watched the river carry away your home?

Truth to tell, we do all these things and more.

People believe us to be unduly negative, destroyers of reputations, hype artists, smart alecks, and sometimes deliberately deceitful when it suits our purposes. They think we falsify and distort and sensationalize to sell papers and boost local and network TV ratings. We are also arrogant and out of touch with ordinary people. We seize on the bad and never tell the good.

That's what many people think of us. But there's a deeper, and more troubling, problem than the manner in which the press operates.

In the last generation, a number of Americans have become persuaded that we in the press are unworthy of trust. Worse, we're bad Americans. We are biased politically and out to advance the careers and fortunes of those who seek to weaken and destroy this nation.

The reasons for this feeling are simple enough. No comparable span of years has produced such stunning shocks to the American people. We have had to be the bearers of bad news. Since President Kennedy's assassination 20 years ago this fall, we have reported one grim bulletin after another--of deaths of major figures, defeat on the battlefields of Vietnam, destruction of presidencies and disgrace of our highest officials.

Nothing seems as solid and secure as it once did. Along with these unsettling events there has been a deliberate attempt to portray the press as the agent of America's problems, the enemy within. If only we hadn't reported such and such, it wouldn't have happened and we'd all feel better.

The political zealots, the hard-eyed haters and the lunatic conspiracy theorists have combined with public figures to poison the well about the press. And they have had undeniable success in sowing distrust about the role of the press and the proper role it plays in American society.

Which brings us up to the present critical and, to me at least, ominous moment in the long history of relations between press and government in this nation.

In the invasion of Grenada we are witnessing what is probably the first "official" war in the history of the United States, produced, filmed, and reported by the Pentagon, under the sanctions of the president. It is a "good" war, conceived in secrecy and carried out in the shadows. All we know about it is "positive," because that is all we are told about it. This goes far beyond wartime censorship of the past. If there has been a comparable total blackout of coverage of a U.S. military engagement on a foreign shore, it does not come to mind.

Throughout our history, the relations between press and government have been of necessity difficult. From George Washington on, every president has had problems with the press. Every president has criticized the way we operate and what we report, especially in times of crisis. Even during the Revolution, before we had a president, Gen. George Washington as commander of our Army was complaining about the information "of an injurious nature," as he put it, that our correspondents were reporting in the public journals of the day. But he and every one of his successors as commander-in-chief understood why the American press had a right to accompany soldiers when they went into combat. All until now, that is.

The Reagan administration's official rationale for banning the press from covering this invasion goes this way: First, it was necessary to protect the secrecy of the mission. Second, it was necessary to ensure the safety of the journalists.

No precedent exists for either. American correspondents have participated in the most secret of commando operations and landed with our forces on countless beachheads. They willingly have taken risks on battlefield after battlefield and many of them have died or been wounded. For all the problems they may have created for commanders and presidents, they performed an essential public function and provided an honorable record in conflicts past.

I will grant the sins and excesses of the American press, don sackcloth and sprinkle ashes on my head for my own considerable mistakes as a journalist, but I also want to shout that a dangerous precedent is being set by this administration. It goes entirely against the best interests of a democratic society, for it is precisely at a time of crisis that the public most needs the unfettered information that only a free press can provide.