I've heard Jimmy Carr tell jokes about all of the groups you mentioned.Yep. If a big theatre of people laugh, the joke has done its job.
People are right in saying Carr wouldn't make that joke about the muslim community, the disabled community, the jewish community or the LGBT+ community by the way. Not because he "wouldn't dare", but because it wouldn't get laughs, therefore would be pointless as a joke. Public opinion on travellers is overwhelmingly negative in comparison to those other four groups where it's really only a small number of people (bigots) who still actively dislike them. The joke is tapping into the fact that he knows the majority of that audience will have that certain disdain, right or wrong, that I'd say over half the British public have. I doubt he'd have any problem joking about the mass murder of any of those other communities if he thought it'd get laughs. But I doubt it would.
Before anyone gets the wrong idea, I'm not commenting on whether or not the dislike of travellers in this country is justified. Just that it's interesting that he had enough confidence in that joke to get laughs that he was willing to tell it on a Netflix special.
Everyone knows what his style is and if he has a show called 'dark material' it's going to be bad so not sure why people are surprised.
I don't even think the joke he has been criticied for was even the worst in the show and his shows that aren't on netflix are often even worse.
I was at the apollo watching him when he ended up on the front pages of the papers the next day for his joke about the paralympics and soldiers in Iraq. It was just another joke that nobody in the crowd was visibly ar audibly offended by.
If you're going to be offended - especially after his show starts with him warning that there will be topics discussed that could upset people - don't watch it!