Reporters who write about the poor, and about the current policy decisions that are making them poorer, learn the art of emotional detachment. A professional hide is needed, otherwise anger can get the best of the reportage. But the other morning, at hearings on food-stamp reductions before the Senate subcomittee on nutrition, Loretta Schwartz-Nobel, a Philadelphia reporter, had to pause in her testimony to fight back the tears.

She was telling the two senators before her--Patrick Leahy (D-Vt.) and Richard Lugar (R-Ind.)--about some of the hungry people she has interviewed in the last seven years.

They included an elderly widow who, after using her Social Security money for rent and utilities, had $30 a month for food. Another was a woman who lived mostly on cheap soup. For a third, a few peas were the daily meal.

The backup services that are thought to be there are not there. Schwartz-Nobel told of a Philadelphia church that has been feeding the neighborhood hungry for two years. A sign posted on the door last month read: "No food today. We have none." In Chicago, a study of 2,000 patients at an urban community hospital found that 44 percent were admitted with nutritional deficiencies.

At Einstein hospital in Philadelphia, an official who helps feed 770 citizens said to Schwartz-Nobel last year: "Now I hate to hear the phone ring. If Reagan gets the cuts he's asking for, we may as well put a tape on the phone and say 'no service available.' I'm starting to feel as if there are no answers."

President Reagan did get the $2 billion in food-stamp cuts he asked for last year, and now the administration is back to ask for $2.3 billion more in reductions. The subcommittee's hearings were called to examine the administration's case.

The case was weak last year and it is weaker now. It rests on the shaky argument that, as a Department of Agriculture official said, food stamps is one of those "automatic spending programs." It must be viewed within the "context of uncontrolled growth."

For a moment, the program does seem to be an extravagant runaway: from less than $1 billion in 1970 to $11.6 billion now, from fewer than 7 million people in 1970 to over 22 million now. But these are selective figures. In 1965, federal food-assistance programs were run in only 110 counties out of 3,000 counties nationally. A decade passed before nearly every county had food stamps.

The growth, occurring when the poor were hawk-eyed by the government to see that they didn't get a spoonful of food more than the regulations allowed, reflected need, not federal generosity. The average meal allotment is 43 cents per person. Someone with no income is allowed 65 cents.

If that was niggardly and if the cuts last year were harsh, the new proposed reductions border on outright contempt for the poor. Estimates from the Congressional Budget Office reveal how hard the already-down poor would be kicked:

* 95 percent of working poor households would be eliminated or reduced.

* 92 percent of the benefits to the elderly and disabled would be eliminated or reduced.

* 85 percent of everyone receiving food stamps -- 17 million citizens -- would have their benefits cut out or cut back.

Ronald Reagan's suspicions about Cadillac-driving poor people chiseling for food stamps have been vented for years. "I heard about this one lady in Chicago. . ." But now that the small amount of fraud in the program has been all but eliminated, he is going after the working poor. A subcommittee analysis shows that working families earning the same amount as families whose incomes are from welfare or unemployment compensation would receive as much as $400 a year less in stamps. This would affect 17 percent of the working families that receive food stamps. It would be a 100 percent assault on the work ethic.

With Loretta Schwartz-Nobel on hand to remind official Washington that weeping about the hungry has a rightful place in the debate, it may well be that only the public's expressed gut-feelings against the proposals can stop them.