I'll mention my father here. First establish his credentials: he was a regular from 1945 to about 1977, used to go and watch City at home and City reserves at Old Trafford post war. He went to Newcastle to watch City win the league in '68 (and got back the following evening as the bus buggered off without them). He's a Blue. Through and through.
He doesn't hate United. Never has. He views them as the other Manchester club and enjoys their success, even when I would express my disdain for them. He's never gone down that route, he remembers the old days.
But Liverpool? My word, the venom he has for them. He's 82 now, but the vitriol and loathing is quite something. Talking about how he doesn't hate the club, but does hate the fans. How they've always been violent and entitled.
I'm a casual City fan. I live in the south because my parents moved down here. I go, oh to maybe 5 games a year. And my Dad loves seeing the City he grew up with succeed. He's thrilled to bits. But he hates Liverpool. Despises them. I guess the point is, this isn't a new thing.