Mr Maginnis's allegation that Mr McGuinness was the chief of staff of the IRA and had authorised killings - a charge he denied - was overshadowed by the fact that the debate was taking place at all on British television for the first time.
In spite of the rhetoric, it will have raised hopes that after consulting businessmen and the community, the Ulster Unionists will respond to the IRA ceasefire by taking part in the cross-party talks in Belfast when they resume on 15 September.
The Ulster Unionist deputy leader had to overcome deep misgivings in the Ulster Unionist Party to sit at the same table as the Sinn Fein MP.
The Ulster Unionists denied before the debate on BBC Newsnight that it would open the way to David Trimble, the Ulster Unionist leader, sitting down at the negotiating table with Gerry Adams, the Sinn Fein leader.
Asked whether he would join the talks, Mr Maginnis said: "One of the responsibilities I have is to find out exactly what Martin Maginnis and the IRA wants ... If they are going to come to the table with their guns, and the threat of force, there can be no progress."
Pressed on whether he would negotiate at the table with Sinn Fein, Mr Maginnis said: "That remains to be seen. We are certainly not going to sit at the table with terrorists. As far as I am concerned Martin Maginnis is the Godfather of the Godfathers of the IRA."
It was pointed out that he was sitting down with Mr McGuinness, and the Ulster Unionist MP said: "I felt it was wrong to let the IRA come on the airwaves unchallenged and there are now enough people who agree with me for me to come here."
The exchanges revolved around well-tested ground, on whether Sinn Fein accepted the principle of consent of the majority in Northern Ireland before there could be a change to a united Ireland, and over decommissioning of weapons.
Mr Maginnis said he was not satisfied with the Sinn Fein negotiator's replies on the issue of consent, but Mr McGuinness made it clear he believed they were principles which they could all bring to the negotiating table.Reuse content