William F. Buckley Jr.'s piece {op-ed, Dec. 18} is a classic example of statistical misdirection. Mr. Buckley implies that the Democrats have nothing of substance to criticize, in terms of either taxes or social spending, concerning the Republican agenda under Ronald Reagan. Baloney!

I do not believe the tax issue can be limited to a discussion of a certain dollar amount or the adjusted percentage increase in taxes compared with that during the Carter administration. The deficit had to come from somewhere. Clearly, it arose in spite of the increase in revenues: it arose because the rise in expenditures outstripped the rise in revenues. The promise of supply-side economics was that the revenue side would increase equally as fast. The problem was that revenues did not increase as promised; that expenditures were increased before the revenue increases were in; and that monies were spent that we did not have. Pure and simple.

Any carping about congressional meddling in the Reagan agenda does not reflect reality, either. Supply-side economics is a paper phenomenon. This administration conducted a national experiment based on paper promises. Congress did not fail us; the paper and those that forced it upon us without careful enough study failed us. The fact is, this country is going down the economic drain. Finger-pointing and rationalizations will not change this awful fact.

As for Mr. Buckley's comments comparing the living conditions of our homeless with those of the Muscovite middle class, so what? That Moscow's apartment dwellers may live more poorly in no way answers the increasing problems of the homeless in our cities. In addition, comparisons of net dollar amounts spent on social programs in the Reagan era relative to the Carter years just serve to mask the real issue, which is not how much money we spend, but how it is spent and how much we should we spend.

Regrettably, caring for the plight of the less fortunate has taken on an ideological bent. The homeless seem to be the lightning rod of the conservative-liberal struggle. Are conservatives less concerned than liberals that working families are being thrown into the streets? I really doubt it.

LAWRENCE TOBIN Columbia

William F. Buckley Jr. neatly sidestepped the answer to the question, "So what can the Democrats fume about?" To quote from his piece: "It is a part of the liberal legend that the reason we suffer so huge a deficit is that Reagan has 'reduced' taxes."

Mr. Buckley goes on to elaborate on how the Reagan administration has reduced the rate of taxation and has still managed to acquire more revenue. He completely ignores the question of how the huge deficit got here in the first place.

If you ask Mr. Reagan he will tell you that Congress is responsible, since it has not cut domestic spending enough that more could be spent for the defense buildup. The president doesn't seem to realize that the preamble to the Constitution authorizes providing not only for the common defense but also for the general welfare, among other things.

Since 1932 I have listened to Republicans fume about how the Democrats are the big spenders. Now the shoe is on the other foot. In seven years, the Republicans have more than doubled a deficit it took the Democrats 48 years to accrue, during which time we survived the Great Depression, World War II, the Korean War, the Vietnam War and a large hunk of the Cold War. How do the Republicans account for their bigger share of the deficit? I think the Democrats have much to fume about.

B. H. GARHART Lusby, Md.