A COMMON ESCAPE hatch through which beleaguered foreign leaders often attempt to flee their critics is the argument that they are doing no more or no worse than what the democratic countries do. In recent days that argument has been doing especially heavy duty. P. W. Botha, to justify his preference for keeping South Africa's racial groups in separate living areas, claims that Ronald Reagan himself "is shoving Indians into reservations and entrusting all the affairs affecting their lives to a single bureau." Wojciech Jaruzelski asserts -- again -- that his imprisonment of Poles for considering a work stoppage is on a par with the punishment of striking American air traffic controllers in 1981. Mikhail Gorbachev, bridling at questions about the Soviet human rights record, warns that he may have something to say about violations of human rights in America.

Each of these charges can, of course, be answered on specific grounds. To Mr. Botha it can be said that Indians are not "shoved" into reservations by presidential edict but given the option of living there. Gen. Jaruzelski needs to know that the American flight controllers were fired by the president for defying the no-strike pledge of their employment contract with the government. Mr. Gorbachev, if he made the usual Soviet-type criticism of, say, the tribulations of Angela Davis, would have to explain why the U.S. authorities have been so manifestly unsuccessful at keeping her down.

None of these specific rejoinders, however, gets to the heart of the matter. What is that? Certainly it is not that the American performance is flawless, which it isn't. Nor is it that many Americans are actively concerned with any hint of the abridgment of the rights of their fellow citizens, although that is quite true. The heart of the matter is that the United States and the other democratic countries, possessing governments based on popular consent and judicial systems based on law, have a legitimacy to their political authority and an independence to their courts that countries ruled by unelected self- perpetuating elites cannot even dream of. The measure of independence still enjoyed by courts in South Africa is the exception that proves the rule.

All this is clear enough to anyone who thinks about it. We observe with some chagrin that not all Americans think about it. Some are prepared to blink away just about any defect in a closed society if it bears a superficial resemblance to a defect in the open American society. But the right approach is to work hard to root out the defects in the operation of American society, while looking with a clear eye at the structural defects in such places as South Africa and the Soviet bloc. Their protests won't wash.