There is an air of serious mental illness amongst these people. I'm pretty certain of that. The seething, intense hatred they have for everyone outside of their bubble is deeply disturbing. The frenetic sabre-rattling towards us over the last few years has escalated to the point that I believe it is not about football. It is nothing to do with us being successful, or being better than them, it's generation after generation of ingrained hatred to those they see as outsiders, being allowed to fester for way too long.
In all sincerity, I don't believe they hate Manchester City, the football club. They just hate Manchester. They probably hate Sheffield, Birmingham, London - in fact any major British city simply because it's not Liverpool. And nobody starts thinking like that overnight: that's why I believe it's generational. Parochialism on that sort of scale is nurtured.
To Liverpudlians xenophobia seems to be a cultural thing.