NEVER HAVE SO FEW cared so much about "the truly needy." If you were a voter from Indiana wandering into the House Ways and Means hearing room Wednesday you would have sworn you'd stumbled onto the annual meeting of the bleeding hearts association, and you would have been hard pressed to pick the geniuses from the phonies. No one speaking on behalf of the Reagan administration could say too much about how the truly needy were going to be just fine with the Reagan budget cuts.

Never mind that it turns out that more than 650,000 families below the poverty line are going to be thrown off the welfare rolls or have their benefits reduced. With the stroke of a pen, the Reagan administration has redefined the truly needy so that the poor need not apply. They can just tighten their belts, pinch a few pennies and figure out some other way to support their families in an economy that is holding steady at a 7.3 percent rate of unemployment. And never mind that the government savings will go to subsidize a $30,000 tax break for people in the $200,000 tax bracket. They, you see, are truly needy because without that tax break, they aren't going to invest their money and save the economy.

They truly needy even got a boost from Rep. John H. Rousselot (R-Calif.). "I'm one of those who want to make sure we don't do in the needy," said he, trotting out examples of fraud in unemployment compensation programs, neatly smearing social programs with the broad brush of waste and abuse.

The occassion for all this hand-wringing was the appearance of Health and Human Services Secretary Richard Schweiker before the subcommittee on public assistance and unemployment compensation. He brought with him a blueprint for halting what he called the "astronomical growth" in our social programs -- somehow making them sound like a malignant disease -- but he, too, with all the earnestness of the convert, assured his audience that the truly needy won't suffer.

He failed to persuade Rep. Fortney H. (Pete) Stark Jr. (D-Calif.), who is obviously having trouble grasping the new definition for the truly needy. "We are going to kick out 680,000 people who are already living below the poverty level," said Stark with a note of amazement in his voice. "How can you suggest that isn't taking away those who are truly needy?"

"You have to take it on a case-by-case basis," replied Schweiker, who isn't proposing anything of the sort. "It depends on how you define truly needy. . . . There are some in that marginal area who will be put from one class to another," he said, with all the compassion you'd expect from a computer.

To be fair, even Schweiker seemed uncomfortable with some of his proposals and he repeatedly said that if Congress can come up with less "painful" ways of cutting spending, then "we'd be delighted . . . We have no pride of authorship in these proposals."

Throwing people below the poverty line off of welfare wasn't the only money-saving suggestion Schweiker brought to the Hill. He also came up with the idea of consolidating some 40 social programs into block grants, cutting their funding by 25 percent and turning them over to the states to administer. Among the least known and perhaps most significant of those programs in terms of long-run social cost was one reforming the American foster care system in which hundreds of thousands of children languished for years in foster homes, often getting misplaced by those running they system. After years in the making, a federal law went into effect eight months ago that provides financial inducements for states to clean up their foster care programs and to get the youngsters back into their homes or adopted. The program seems to be working. yEstimates are that it could save Los Angeles more than $17 million in foster care costs.

The Reagan administration wants to roll this into a block grant, cut the funding and kill the program," says Rep. William M. Brodhead (D-Mich.), noting that it passed with overwhelming liberal and conservative support. "This is a very carefully liberal and conservative support. "This is a very carefully structured bill. You take away the incentive to perform and you're back to the old syste." Why does the administration want to destroy a program that can save the government money? "It's a case of ideology overcoming pragmatism," says Brodhead. "They don't like the idea of the government holding out the carrot to the states. They don't like the idea of the government holding out the carrot to the states. They think the states can solve the problem better than the federal government, but all the studies show they don't and they didn't."

No one is in favor of waste and fraud and no one wants to pay income taxes to support people who can work. But there is a difference between a government that's being a sucker and one that has compassion. And there is a difference between a government that is effectively trimming waste and fraud and indefensible largess from one that is sacrificing effective, socially responsible programs on the altar of ideology. Pete Stark was clearly troubled by all this. So was Rep. Charles B. Rangel (-N.Y.) who noted wryly that no one has cut his Korean War benefits. He understands that with his $60,662-a-yea congressional salary, he isn't truly needy, but he also understands compassion for those who truly are.