Thank you for the replies so far which on the surface and possibly more seem to me to be quite varied. However, perhaps there is consensus that what is different in this case is that it is/was directed at someone rather than being attempted more generally on a stage. Yes - I have had a lot of trauma in my life. I take the point that people's reactions to things differ and that for some difficult real jokes can be therapy.
On a different point, I have had a reply to my e-mail from the Lib Dems - they honoured their word on their website which was to seek to come back within 24 hours - and what they have said is quite interesting. They wish to, quote, "reassure" that nothing will be going into people's letterboxes with the phrase "Bollocks to Brexit" on it. What this says to me is the phrase was picked to get maximum newspaper publicity.