What can he say?
The relevant part of those answers he gave, is this bit
"But I'm not going to sensationalise in interviews something that could then be used to the detriment of the peace process and to the detriment of my colleagues within government."
Means what ever he did, he is not going to talk about it in any detail and the easiest way to avoid further follow up scrutiny to sensational questions, is just say no and keep saying no, whether it's true or not
12 years after the GFA was signed there is still a peace in progress and that process is more important than this shindig. How could he sit down and work closely with unionist leaders for years and at the same time regale newspapers, tv interviews with anecdotes from his days as an urban gunman, how then could those unionist politicians face their constituents and explain their participation in the peace process?