City tour guide? You need to check your facts on that and so much more. Yes I have been on the away end at Anfield (away corner actually back then was where they had terracing for away fans of course!), and know all about rivalries, hence my comments. In 1991 I published The Pride of Manchester (history of Manc derby) and have researched every single derby game. I know about the acid bottles thrown over the roped barrier on the Kippax on derby day in the 1960s and early 1970s. Violence, sadly, was always a part of life at football grounds - I remember Everton fans lying in wait for City when we returned to Victoria Station from Blackburn in 1984-85 on the same day they'd played MUFC, as well as many other incidents at Elland Road, Anfield and elsewhere. But violence doesn't mean a derby style rivalry, if it did then City's biggest 1990s rivals were Millwall and United's greatest rivals of the 70s would be Leeds - or City if we're talking about violence, pitch invasions and so on.
A derby rivalry is multi-faceted and involves all sorts of scenarios such as the more banter style pranks that used to be performed in the 1920s - I have some great stories of how Utd fans broke into Hyde Rd and painted the fence blue on derby day for example.
Utd-LFC is a rivalry about success and it was made prominent by Fergie. Before Fergie it was intense at times, but not regarded as a derby (other than the typical old Lancashire derby comments). Utd & LFC fixed a game for gawd's sake - would you do that with your biggest rivals!
That's the type of literary owning that only a professional writer can dish out. Impressive.