They'd never vote for a scouser in Manchester. They certainly wouldn't make him Mayor of the city.
Are you a Scouser and have you worked in Manchester?
I'm not originally from Liverpool, but have worked in and around Manchester/Greater Manchester for around 30 years on and off. There is a huge bias against Liverpudlians, The City and the Club. There are, of course, also plenty of nice people in and around Manchester and there are some absolute weapons (The same in Liverpool and any other City or even town or place, obviously)
I've also seen anti-Scouse shite (Some directed at me) in the five or so years I've worked down South - again - the majority of people are nice, but some absolute weapons.
The stereotype of Scousers being lazy, thieving, cowardly shithouses is very evident. If you have a Scouse accent or people see you as Scouse then you'll see it. I've had some physical issues around some of these events, but luckily managed to deal with them in an appropriate way. The thing I like is that for every knuckle-dragging inbred Yorkshire or Southern or Manc shithouse, most of their mates are fine. Usually just one gobby fucker kicking it off.
You see an escalation of most things - an amplification - when you are in a crowd situation - as you know if you've been to the match - that's why we have a problem with the shithouse poverty and tragedy chanting that is very evident when we play certain clubs.
If you haven't seen it or you aren't a Scouser or you don't Live in Liverpool then it's probably not something you can comment on one way or the other I'd say. It does seem odd to me that you don't seem to believe it's even a thing? Do you not have any Scouse mates?