TUCKED AWAY in a small corner of the administration's 1984 budget are some strikingly mean-minded proposals to make the nation's poorest families poorer yet. The affected program is Aid to Families with Dependent Children. Even before the Reagan administration began its assault on social programs, welfare aid for families was a small and shrinking part of the federal budget. AFDC benefit levels are set by state governments, and there is no automatic adjustment for inflation. Since welfare families have no powerful defenders in state legislatures, average family welfare payments have been allowed to decline by more than 30 percent in purchasing power since 1970.

Federal budget cuts made in the last two years have accelerated these losses. AFDC has been reduced by 13 percent as a result of cuts made in that period. So far the biggest losers have been working poor families, most of which--contrary to administration suggestions --had incomes below the poverty line despite their work efforts. Now the administration proposes to cut federal AFDC spending by another $700 million.

Now, if you want to hear about truly dumb and mean attempts at savings, consider these. They would come from such things as reducing welfare benefits if families share quarters with friends or relatives, or if minor children manage to earn a little money. Families would also be denied help if the father left home to look for a job. Work requirements would be strengthened (in an economy in which 11.4 million people can't find work), but the already underfunded WIN program, which helps welfare parents find jobs and training, would be eliminated.

These changes might make some sense in a country with full employment and an adequate level of welfare aid. But how can anyone possibly consider cutting welfare for, say, a family of four in Texas whose total cash income is $140 a month just because that family is sharing living quarters with someone else? How else could they survive? And who would be so mean as to deny a child in that family the fruits of his labor if he is lucky enough to find a job? What sort of rationale could justify such rules?

Linda McMahon, the administration's welfare chief, may have supplied a clue to administration thinking on these matters in an interview with The New York Times last fall. In justifying the administration's previous cuts, she noted that their effects must be tolerable because "We're not seeing riots. We're not seeing people rushing the doors of Congress and the White House."

The idea that a scattered group of subsistence workers would jump on jets and storm the seat of government has its amusing aspect. Not so the notion that it's okay to take help from the poor just as long as they don't take to the streets and inconvenience the rest of the citizenry. Is there no longer anything to be said for simple human decency?