As far as Ralph McTell is concerned, and as a fan for many many years (and who's got to know lots of other fans), I've never heard of an incident at a gig where he's lost his temper, at least not recently! I know that it happened more than once during the tour after Streets of London became a hit,(mid 70's) but he was later diagnosed with depression, and said to be on the verge of a complete nervous breakdown at the time! I've heard that he is fussy about some things, however - a few years ago apparently he lost his temper with a theatre manager who said that it didn't matter that the wheelchair access to the auditorium was blocked with rubble - something that it's worth loosing your temper over, I reckon!
Have to say, he's always polite and patient with his fans, though, and frequently makes a point of thanking his tour manager/sound engineer during shows - and apologising to him if he over-runs!

(Is 'crabbiness' the same thing as 'fussiness' or perfectionism when it comes to giving a performance? Though I'd hope any performer that I pay to see is at least a litle fussy about getting things right, I imagine that perfectionism could easily become crabbiness!)