I find it strange that so many comments express a measure of understanding for this 4th dan female instructor. Had it been a 4th dan male instructor doing the same thing, I'm sure this board would be filled with strong condemnations of his actions.
Personally, I find that kind of behavior absolutely unacceptable from anyone at any rank. I know I've been angry a couple of times on that mat. Frustrated more than a couple of times. I've never lashed out at my uke or had anyone lash out at me.
Still, before forming a judgement, it would be helpful to know how often this particular student loses her temper. Is that particular 2nd kyu really hard on all his ukes? Are there other background facts that would put this incident in context?
More to the point: Edward, why did you post this here? What sort of response are you looking for? (These are honest questions, I'd really like to know.)