I think it is simple ... they are trying to scare people to make it easier to take away their rights.
It is also a way for them to distract people from all the junk that goes on in the UK. When all you read about is what a bunch of savages Americans are and you never hear anything bad about the UK, you start to think your government is awesome.
Thats my guess.
I think also it enters the dimension of thinking it is "the other". Something only the stupid or sketchy Americans do. Had a conversation with international colleagues. Of 3 Americans all owned guns but it surprised them. None are crazy nuts and they would have never known unless we told them. I was the only one they knew before and that was around shooting trap which is just glorified sporting equipment to them.
Did I joke I can own it because of my British colleagues forefathers... Obviously. Of course he is more wrapped up in the shame of his own sibling supporting BREXIT and Boris.
To be fair I met one girl from MA on OKC years ago who was freaked out that her boss owned a gun. She didn't understand why someone bragged on their profile that he owned a full auto gun, had to explain to her that guy must have MONEY. Shit ain't cheap.