It is possible that Mr Sallis is perfectly amenable nearly all the time, but was insulted by a journalist who had not done research in advance of her interview.
Speaking as a journalist, I think it is only courtesy to research your subject before an interview. It is respect fof them and their craft, and because they have agreed to give up a portion of their time, it is only proper that you should know about them and their work.
I have seen a couple of occasions where interviewees have lost patience with the sheer stupidity of questions being offered, which show quite clearly that the interviewer has no clue about them, or what they do.
Similarly, I have been complimented about my research, and been told that it is a rarity in this day and age.
So I would be prepared to believe that the old gentleman was being offered nonsense, and was offednded, and said so - perhaps more sharply than necessary, I would never condone upsetting anyone to the point of tears, but it is a lesson to learn.