WHEN modern Germans quarrel about politics, they seldom hit each other. In an old-time Saalschlacht (hall battle), the two sides of an audience would smash each other up with chairs. But nowadays they only stand nose to nose and scream.

I went last week to a meeting in Bonn organised by the SPD (the Social Democrat opposition), to debate 'The Left after Maastricht'. We were leaving when an ugly political row suddenly exploded outside the doors. Things were said which in Britain would have led to bloodied noses. In Bonn, it stayed with words . . . just. But they were frightening words.

It started as no more than banter among party officials and MPs. Then, without warning, the man on my left accused the man on my right of being a crypto-Stalinist authoritarian who had gone secretly crawling to the East German leadership. The man on my right shouted that he had acted honourably by urging the Communists to expel dissidents rather than imprison them. His accuser, shoving his face to within an inch of his adversary's, bellowed that he had sold out the East German resistance behind their backs, because he secretly wanted the dictatorship to continue and because - like all the cowardly scum who had been the curse of the party through the generations - he was terrified of any kind of revolution, socialist or democratic. At this, a third SPD figure screamed that the accuser was a destructive political lunatic who had begun as a sympathiser with left- wing armed terrorists and murderers and now covered his tracks by posing as an ultra-right anti-Communist hero.

Then, equally suddenly, it blew over. Growling, they got into their waiting limousines and were driven off. For my part, I walked a couple of miles back to the hotel trying to analyse my own horror at this scene.

What Germany needs now is not so much a new government - though it needs that desperately enough - as a new opposition. But the SPD is sick in its soul.

In the post-war period, especially under the leadership of Willy Brandt and Helmut Schmidt, the Social Democrats became the most important political party in Europe. This was not only because of what it did in government, for it held office seldom. It was also because it was a sheet-anchor of patience, democracy and hope, keeping West Germany - and therefore Western Europe - firmly in place.

Because of the SPD's challenge, West German conservatism developed into Christian Democracy, and not into right-wing nationalism or the narrow- minded class selfishness of British Toryism. Because of the SPD's refusal to demonise or to hate, West Germany's rigid anti-Communism softened into the Ostpolitik: the use of contact and dialogue to relax the dictatorships of Eastern Europe. For the young, the SPD has seemed maddeningly reformist. But the novelist Gunther Grass was paying the SPD the highest compliment when he compared it to a snail.

Where is the SPD now, when we all need it so badly? If it had been in power, the Social Democrats would surely have shown less hesitation in throwing the state into the defence of the refugee hostels. With an SPD-led government, neighbours (especially France and Britain) would be less paranoid about 'German domination', while Germany might well have avoided bouncing the European Community into recognising Croatia and Bosnia.

The SPD, disastrously, failed to understand in late 1989 that the full and rapid unification of Germany was unavoidable. Chancellor Kohl, in contrast, grasped this instantly and thereby rescued his own and his party's political future. But the Social Democrats saw much more clearly than Kohl how difficult it would be to knit the two societies together. Now, as the eastern German economy plunges further into ruin, we can only regret the SPD's alternative plans: no one-to-one rate for the Ostmark against the Deutschmark (a mad stroke of hubris which smashed East German industry's competitiveness), and a much more gradual transition from 'state socialism' to the 'social market economy'. If those policies had been followed after 1989, German interest rates would not now be strangling the world.

But all that is vain 'iffery', and the SPD is in bad shape. It has a new and outwardly impressive leader in Bjorn Engholm. It has electoral wind behind it, as Chancellor Kohl's government flounders over how or whether to mount a financial rescue for the eastern Lander. And yet the party lacks faith in itself.

All socialist parties quarrel boisterously and publicly, as the Labour Party does. But the anger in the SPD is more poisonous. The party is maimed because it has lost its moral self-respect. As that row in Bonn showed, there is a sense that everyone is befouled by some discredited past belief or association, that nobody is clean enough to be taken at face value.

To me, as an outsider who has respected the SPD for 30 years, this is insanity. It is not the SPD that is being revealed by the Stasi files as a warren of informers, but overwhelmingly the right-wing parties. And there is nothing for the SPD to be ashamed of in the policy of 'change through rapprochement' towards the Communist states. That policy calmed Europe down, until Mikhail Gorbachev could risk letting the Soviet empire choose its own path.

The irony is that the SPD, which was profoundly anti-Communist, has been maimed by the collapse of Communism. The party came to rely on the survival of its enemy. Externally, the Cold War gave it a role as mediator and peacemaker. Internally, it made the SPD priceless as the guarantor that the West German working class would never be infected by Stalinism. But when Communism collapsed, it was not only the Christian Democrats but also those who emerged from East German prisons who turned on the SPD and said: 'You treated our jailers and tyrants as morally fit partners for dialogue] Why did you not first talk to us, or were you afraid that our masters would not ask you back for another round of cosy chats?'

That version was a travesty. But it had just enough truth in it to cause the present awful mood of guilt and self- hatred that is still paralysing the SPD. The party feels that it failed to defend democrats in their time of need. Now, disastrously, Social Democrats lack confidence that they can defend the working people of Germany in another hour of need; that they have the moral right to give leadership to the hundreds of thousands in eastern Germany who are losing their jobs or facing bankruptcy, or to the young whose apprenticeships are being abolished, leaving them easy prey for neo-Nazi recruiters.

This should be the SPD's hour. At any moment the exhausted Kohl government may offer terms to the opposition: a common programme, or even partnership in a grand coalition. Kohl is bogged down on the economy, on how to reduce the inrush of asylum- seekers, on whether the constitution should allow German troops to operate outside the Nato area.

The moment approaches when the Social Democrats could take their share of responsibility. But the party seems unable to act. Willy Brandt spent much of his life making the SPD electable. As that life nears its end, it is his, and Germany's, tragedy that his party has apparently lost the will to govern.