Is there something about the air on Pennsylvania Avenue that causes Gary Bauer, assistant to the president, to believe, after seven years of the biggest government spending in American history, that defense spending doesn't count as government spending? To quote Mr. Bauer {"Don't Desert the Revolution Now," op-ed, Dec. 8}: "An 'imperfect' Reagan presidency is not the enemy. Rather, it is the resurgent liberalism that hopes to discredit the president and conservatives in 1988 and to put the country back on the path of big government."

There hasn't been an administration in American history, Democratic or Republican, that has spent as much money as the Reagan administration has. This administration has set a new standard for the term "big government."

When Mr. Bauer proudly points out that, because of the efforts of the Reagan administration, "federal programs no longer expand," the sad truth is that he is talking about programs to help abused and neglected children and their families, the poor and the increasing numbers of homeless people in this country.

One out of five children today lives in poverty. In 1986, 2.2 million children were reported to be victims of abuse and neglect. A nationwide study conducted by the Child Welfare League in 1986 found that for every 10 homeless adults studied, eight children were affected.

During the Reagan years the defense budget has increased by $155 billion, while the major source of federal funding for child protective services, the Title XX Social Services Block Grant Program, has been frozen since 1984 and cut by nearly $300 million. Federal appropriations for low-income housing assistance have fallen by more than $20 billion. In 1984, Medicaid served approximately the same number of children as in 1978, despite the fact that the number of poor children increased by one-third.

Mr. Bauer can keep calling the recent major housing bill, which passed nearly unanimously in the House, one of the "budget-busting pork barrels." But it's time he realized that the $3.2 billion for the strategic defense initiative and the nearly $30 billion for B-1 bombers come from the same pot of money. A fraction of those amounts could, among other things, help prevent child abuse and homelessness and finance a comprehensive health care system for all of America's children.

DAVID S. LIEDERMAN Executive Director, Child Welfare League of America Washington