The urges of rock fans are primal. They have been known to riot, occasionally to kill, and in East Berlin, of all places, they recently battled police to hear a Genesis concert on the West side of the infamous wall. They shouted, "The wall must go," which is music of its own kind; "Down with the pigs," which is a refrain heard here on occasion; and then, most troubling of all, the name of their new hero: "Gorbachev, Gorbachev." He is no singer, but he's singing some sweet song.

There was a time when rioting East bloc youths might have shouted a different name -- say, John F. Kennedy's. It's not hard to remember when the name of the Soviet leader would never have passed their lips, except linked by a verb to an obscene word.

The problem is that the Berlin incident, while unique in some ways, is typical of the changes wrought by Mikhail Gorbachev in a very short time. In Western Europe, public opinion polls show significant numbers of people consider Gorbachev, not Ronald Reagan, the superpower leader most interested in peace. In Britain, Reagan's standing is so low that his klutzy pre-election embrace of Margaret Thatcher proved an embarrassment to her.

On the continent, many Western Europeans mistakenly think it was Gorbachev, not Reagan, who first came up with the so-called zero option as a way of eliminating nuclear missiles. Their confusion, while lamentable, is understandable. Arms-reduction initiatives seem more characteristic of the dynamic Gorbachev than the ideologically rigid Reagan. And, anyway, when Reagan offered the zero option in 1981, it was widely believed to be nothing more than a ploy -- an offer the Soviets were not expected to accept. Until Gorbachev, they didn't.

Too much can be made of this -- but not easily. The shift of European public opinion and the admiration of a Soviet leader by East German youth represent a real reversal for the United States. After all, it's America that's a vibrant democracy and the Soviet Union that's politically repressive and economically stagnant. And yet in Europe, where it may count the most, many people cannot discern a difference between the leaders of the two countries.

Washington is just beginning to feel a twinge of uneasiness at this turn of events. (One of the surveys of European public opinion was secretly commissioned by our own government.) The town has been riveted on the shenanigans of Lt. Col. Oliver North and his secretary, Fawn Hall. But sooner or later, even Reagan administration officials will connect the shift in European public opinion with what's happening in the Senate Caucus Room.

The ultimate folly of Reagan and his most zealous followers is that they have chosen to fight wars that matter least. The contra phase of the Iran-contra hearings is just one aspect of the Reagan Doctrine. But the Reagan administration is also fighting on other fronts -- Angola and Afghanistan, for instance -- and has not shied from "showing the flag" -- usually by affixing it to a rifle barrel. Its most signal victory to date has been the "reflagging" of Grenada, and while the effort in Afghanistan cannot be equated to the one in Angola, the United States under Reagan has nevertheless left the impression that it has a mighty quick trigger finger.

Perceptions are important. They are particularly important in Western Europe, where governments are democratic. Public opinion must be taken into account. An electorate that is increasingly beguiled by Gorbachev and wary of Reagan is not likely to support leaders who wish to stand fast`against the Russians`or who are rightly skeptical of Soviet intentions when it comes`to, say, arms reduction. Already Western Europe and Japan have refused to materially support the United States in the Persian Gulf -- and it's their oil, not ours, that's at stake.

` nald Reagan came`to power prepared to do battle with an aging and`ideologically ossified Soviet leadership. He adopted some of its tactics -- for instance, the use of proxies to wage wars -- but seems not to notice that new guys have taken over. Covertly or overtly we fight theold wars, rattle billion-dollar sabers and send warships to do the workof diplomats, while in the streetsof East Berlin, rock fans shout the name of Gorbachev. It's a foreboding sound of the future to which the Reagan administration has turned a tin ear