A joke that is not funny is not a joke - but the audience laughed. I can only think that audiences often laugh because they do not want to be judged as not "getting it." There can be no other reason for them laughing at this.
Did the "joke" open up awareness of the plight of Gypsies and Travellers, both in the past and now? Was that his motive? I suppose we are all talking about it which could be seen as raising awareness; or it could be that it is reinforcing existing prejudices.
I worked for 10 years on the Travellers Times - a national magazine for Gypsies and Travellers - as project co-ordinator, photographer and picture editor. During that time I met many Travellers, some of whom I was proud to call friends, and others that I was wary of - much like non-Travellers. There is no way that I would see a "joke" that applauded the slaughter of innocent men. women and children as being either funny or acceptable in any way.
But he knew what he was doing, and I do believe that anyone who might think this was a suitable thing to joke about is seriously out of order. And I find the idea that he was simply "consciousness raising" implausible. I suspect that he is in fact on the wrong side of the law. It will be interesting to see where that leads.
What also caused me concern is that his friend Victoria Coren-Mitchell took to twitter to defend him as being a "decent" person. I had always rated her highly.