As a British citizen, I know it’s more complicated than I stated on a quick comment for a US web site. But I appreciate your expansion on my quick explanation for American Readers - who usually find it incomprehensible that the public have the right to cross “private” land.
FWIW, I agree that it’s quite likely the muppets in the video were riding on a footpath rather than a bridalway, although as a mountain biker (who follows those rules when in the UK) I have seen plenty of blocked bridalways. And even if they weren’t, damaging the farmer’s fence through stupidity is not the right way to deal with it.