While I'd always expect some boos and raspberries from a sporting crowd for any politician, I'd doubt if too much can be read into this. Here's what a trawl through Google News threw up from a regional paper serving the West Country heartland of Rugby Union (not a traditionally left-wing part of the country).

As for the "English culture is under attack" bit, it's worth remembering that London's native culture has not for a very long time (if ever) had much to do with rural traditions such as Morris dancing and such. Music Hall and Cockney has been much more the thing, and in a real sense this is the tradition within which Ken Livingstone fits in his style. And the street Cockney culture was very much based on immigrants into London, both from the country, but also especially Irish and Jewish and others from further afield.