The Reagan administration is being pilloried for its now-abandoned proposal to tax unemployment compensation.

That strikes me as unfair. It is a well-established principle of government that the tax structure can be used to encourage behavior that is in line with public policy and to discourage behavior that isn't. The tax code allows deductions for charitable contributions because private giving is in the national interest. It allows an extra tax on cigarettes because smoking is not in the public interest.

Clearly massive joblessness is not in America's interest. And yet there was hardly any public support for the proposal to alleviate the problem by taxing unemployment checks -- an idea which, according to White House spokesman Larry Speakes, was calculated to encourage "a lot of people to get off unemployment and seek jobs."

If this eminently sensible idea was thrown out as a result of political opposition, can't you just imagine what other forward-thinking proposals may have been tossed into the White House trash bin?

I can just see the memo from Health and Human Services Secretary Richard S. Schweiker: "There is no question that in the days before Medicaid-Medicare, fewer poor people sought medical treatment. Oh, they might have gone to the charity hospitals for broken bones or ruptured appendixes or massive strokes--the serious stuff. But the private hospitals and clinics and doctors' offices certainly were not cluttered up with poor people seeking treatment for such trivial complaints as hypertension, palpitations or pneumonia.

"We shouldn't actually forbid their seeking medical attention; that would make us vulnerable on the 'fairness' issue. But if we treat the cost of medical care as income, and then tax it, it would force a lot of low-income people to deal with their own little ailments. This would be a healthy thing for them and, incidentally, it would save us a few big ones in the budget."

Or Interior Secretary James G. Watt: "As you no doubt have observed, Washington, D.C., has a lot of bums. I don't mean Teddy and Tip. I'm not even talking about Dick Schweiker's welfare queens. I mean the truly bummy: the homeless, jobless men and women who sleep on steam grates within a stone's throw of the White House.

"The presence of such people gives tourists the impression that the president's economic program isn't working. The problem, as I see it, is that the steam grates provide free warmth. If we imposed a tax--call it a user fee--on the steam from those grates, I am convinced that a lot of these bums would get off their duffs and move into condominiums like decent Americans."

Or Social Security Commissioner John A. Svahn: "Social Security is going broke for one key reason: too many people are getting old. If we imposed a graduated tax on each year above, say, 60, a lot of people might decide that getting old isn't such a great idea. And if they insist on getting old anyway, the tax would help to offset the cost of the Social Security benefits."

Or HUD Secretary Samuel R. Pierce: "One of the things that keeps hurting this administration is the reputation-- completely unjustified, of course--that we are insensitive to problems of race. Most of these complaints come from black people who, in addition, are driving us crazy with their demands for affirmative action programs and minority contracts, the whole schmear.

"I have been giving this matter a great deal of thought, and it occurs to me that one of the key reasons for our situation is that we make it too easy to be black. What I am proposing is that we consider imposing a tax on dark skin. If we make people pay for the privilege of being black and having access to minority-oriented programs, a lot of them will say to heck with it. Naturally, if black people could be persuaded to stop being black, most of our racial problems would disappear."