'A 10-year-old girl has been shot dead in Gaza by the soldiers of the army of Israel,' he thunders, raising a claw- like hand for dramatic effect, and driving home his point with a fixed stare.
Since the 1967 Six-Day war, Professor Leibowitz, born in Riga in 1903, has been predicting that the Israeli occupation of the West Bank and Gaza Strip would lead to Israel's moral degeneration, to a growing 'bestiality' on the part of the army.
His prophecies, he says, have come true. 'It was unavoidable that such atrocities as this would come about. It is the mentality brought about by accepting the violence of nationalist politics.'
The deportation of 413 Palestinians was 'a terrible mistake', he says. 'A moral defeat for the government.' But again, he adds: 'It was absolutely unavoidable. If we maintain the violent repression of people they will revolt and commit terrorist acts. And we will use all means to suppress this . . . The moment nationality becomes the highest human value that is fascism.'
It is hardly surprising that Prof Leibowitz's views should outrage most Israelis, particularly the right wing, the settlers, and all who rally behind the banner of Eretz - or greater - Israel.
What is surprising is that after all these years of listening to him slaying their sacred cows - arguing for the separation of religion and state, for soldiers to refuse service in the West Bank and Gaza - Israel has not learnt to assimilate his views. The recent announcement that Prof Leibowitz was to be awarded the prestigious Israel Prize for his life's work - he is a scholar of chemistry, philosophy and medicine, and editor of the monumental Hebrew Encyclopedia - caused a political storm verging on hysteria.
At first, he took the attacks in his stride. But when the Prime Minister, Yitzhak Rabin, announced that he too opposed the award and would boycott the ceremony set for April, Prof Leibowitz said he would turn it down.
Commenting on the uproar, he says: 'Many people see me as a traitor. What I am saying to them must amount to treason. That is understandable. This cleavage exists here and has for many years.' What angers the majority of Israelis is the emotive language Prof Leibowitz uses to make his points: comparing the settlers to 'Judeo-Nazis', and declaring that Israeli undercover army units are no better than Hamas, the Islamic Resistance Movement. But Prof Leibowitz - a pious Jew - does not see himself as particularly radical. And, shorn of colourful vocabulary, his views seem hardly more extreme than those of the doveish members of Mr Rabin's own cabinet.
Until 1967 the fault was all on the other side, he says: it was the Arabs who prevented the 1948 partition and then invaded Israel. It is only since 1967 that Israel has become the oppressor.
And he stresses that his motivation is to save Israel, to restore the state to the moral high ground by ending its corrupting occupation. He is not primarily interested in campaigning for Palestinian rights. 'It is not a question of liberating Palestinians but of liberating the state. That is important.'
Whatever the attempts to demonise him in recent weeks (he has been described variously as mad, bitter and disgusting), he says a substantial minority of Israelis agree with him. And this gives him hope for the future.
Prof Leibowitz is prophesying again - on a more positive note. 'The direction of Israeli politics is changing, which means there is a chance for a voluntary agreement between the state of Israel and the PLO. That is a possibility.
'What is more probable is that the partition will be effected not by voluntary agreement but by pressure of the United Nations - which means the US. There is this chance now. Five years ago there was no chance for an agreement at all.'