The announcement of the lifting of the excommunication of the four bishops illicitly ordained by the late Archbishop Marcel Lefebvre has been received badly for two main reasons. The first is the impression given that Pope Benedict XVI is so determined for the organisation that they lead - the Society of St Pius X - to be reconciled with Rome that he may have underplayed the significance of its opposition to some of the key teachings of the Second Vatican Council. But apprehension on this account has been overshadowed in the mass media by a second impression, based on reports of the horrendous views of one of the four, an Englishman named Richard Williamson, with regard to the Jews. He has publicly questioned whether six million Jews died in the Holocaust, and denied the existence of the Nazi gas chambers.

The breakaway of Archbishop Lefebvre and his movement was widely interpreted at the time as being connected with the preservation of the old Latin Mass. The recent re-establishment of the Tridentine Rite as an alternative form of Mass by Pope Benedict has drawn most of the poison from that issue; the rest will come when the Society also accepts, as it surely must, that the post-Vatican II form is equally valid. But not far below the surface of the Lefebvrist movement have lurked some rather more disturbing views, not only its commitment to an ancien-régime style of Counter-Reformation Catholicism, but also to a virulent brand of Catholic anti-Semitism which has a long and disgraceful history, particularly in France (where the movement is strongest).

Bishop Williamson's recent remarks have to be read in that context. The Lefebvrists reject, for instance, the teaching of the Vatican II decree Nostra Aetate, including its key repudiation of the charge of "deicide" (literally god-killing, because of the supposed Jewish role in the death of Jesus). Lifting the excommunication of someone like Williamson, while he is still publicly propagating his bigoted opinions, sends an appalling signal to the world in general and to Jews in particular. To say of these opinions that they are "totally unacceptable", as the Bishops of England and Wales did in a statement this week, hardly does justice to them. They are evil.

Nostra Aetate is not the only Vatican II document the Lefebvrists contest. They do not like its key document Lumen Gentium, which sets out the basis for a modern constitution for the Catholic Church. They have rejected the decree on ecumenism, which brought an end to the post-Reformation conflict between Catholics and Protestants worldwide; and they rejected the decree on religious liberty, one of Vatican II's most radical departures from previous positions which was, for instance, a flat contradiction of Pope Pius IX's Syllabus of Errors. With such documents as these, Vatican II created a new consciousness of what it was to be a Catholic. To be told by the Society that one of its main aims in seeking the lifting of the excommunication is so that it can work towards the rejection of that consciousness and the restoration of a pre-conciliar style of Catholicism is divisive and offensive. If this is the baggage they propose bringing with them, they would be better left out in the cold.

As a good shepherd, Pope Benedict has to take seriously Christ's injunction to seek the return of lost sheep. But it is far too soon to see the Society of St Pius X in the guise of the Prodigal Son. That requires some evidence of repentance. As the Pope made clear on Wednesday - unfortunately a little too late to head off the damage to Jewish-Christian relations that the earlier news had caused - the lifting of the excommunications has to be followed by full submission to the Church's teaching authority, including Vatican II (and therefore including Nostra Aetate). He emphatically denounced the hatred of the Jews that led to the Holocaust, and to its subsequent denial. He acted towards the Lefebvrists out of "paternal mercy", he said. But it is clear he will insist on them swallowing some pretty strong medicine before their schism can be regarded as healed, and the odds against them agreeing to do so must be enormous. If he had made that clear earlier, a lot of the damage to the Church's good name could have been avoided.