The Right-Wing Antipathy to Trigger Warnings

I was chatting to John Cleese on a podcast about this. We should explain things like Jimmy Carr just for non-British audiences, what he said. He does a whole sequence of how far can you go in telling jokes that effectively violate every single convention of human decency. I've never really understood the right-wing antipathy to trigger warnings which seemed to be quite sensible. If there is something you find distressing, and we could never know what those things are, warning people in advance seems to me simply like a courteous and reasonable thing to do.