Former Methodist president and decommissioning witness the Rev Harold Good said he was approached last year about observing IRA weapons decommissioning.
Rev Good, in an interview with BBC Radio Ulster at the weekend, said he was not offended by claims made by DUP leader Ian Paisley that the IRA had "appointed" both witnesses and that this had made their independence and testimony questionable.
Dr Paisley said both the Rev Good and Fr Alec Reid had been "IRA nominated", and that this had therefore put "a very big question over what has taken place" regarding IRA weapons decommissioning.
Mr Good felt confident he had not been duped by the IRA and said he had "never felt as right about anything as I felt about this".
He added he had been "overwhelmed" by the reaction to his role in the decommissioning process from some unionists and Orangemen.
He strongly defended the role played by himself and Fr Reid.
Asked if there was a risk of his being tricked, he said: "I don't believe I have been, not for one moment, but we have to be prepared to be fools for the sake of the greater good."
UUP deputy leader Danny Kennedy and North Down MP Lady Sylvia Hermon have backed Rev Good following the DUP leader's criticisms.
Mr Kennedy, who is from Bessbrook in south Armagh where the Rev Good first ministered, said it was a matter of regret "others" had questioned the clergyman's integrity.
Fr Reid said of the former Methodist president that it should be a matter of pride for the Protestant community that a man of the Rev Good's integrity had come from their midst.
Rev Good described the meeting at Stormont last Thursday between himself and a DUP delegation as "amicable" and "frank".