I wouldn't dissagree with that in the slightest and I'm pretty certain it'd be a valid and justifiable defence. But it opens up a whole new can of worms doesn't it? HM Queen guarded by downgraded nutters etc.
What is more worrying is that he didn't use his brains either, and did it it infront of the world (although understandable behaviour for a woodentop). The Sgt of The Guard should have allocated a man to quietly follow them back to their hostel and then torch it as they slept.
On a larger scale, where would we be if everyone was able to snap simply because some insignificant scroat took the piss out of them?
disclaimer: only joking about the torching the hostel bit