This is a matter of opinion an ddifficult to answer.
Firstly, there are few people left who would really consider themselves cockneys and the cockney accent is rarely heard. I suspect that most Londoners don't really think of Northerners either positively or negatively.
The answer may well be different if you consider what London football supporters think of supporters of Northern teams.
the war was over,then the northerns called the southerns rebels cuz they were not strong and the northerns hadn't died
No. People from London are called Londoners. 'Cockneys' is an outdated expression.
Northerns cricket team - Zimbabwe - was created in 2006.
northerns
No, people from Leicester are not Cockneys. Cockneys are traditionally associated with East London, particularly the working-class neighborhoods in the East End. Leicester has its own distinct culture and dialect, influenced by its diverse population, but it does not share the specific traits that define Cockney speech or identity.
Copperheads
Copperheads
The East End district of London.
slavery
No. Consider that not all the Man U players are from England, and a number of individuals from the home country of a given player will root for Man U because their countryman is playing for that side. There are others still (non-cockneys) who like this group of footballers, and will be fans with no other motivation than they like the way the lads perform on the pitch.
Yanks, Yankees
The Yankees - or "Bluebelly".