Technically he's correct. He's from Liverpool, therefore he's a Liverpudlian. Bear in mind that it's a London-centric paper. It would be easier if the national collective was to refer to supporters of the darkside as RS, rather than daub all of us who hail from the city as Liverpudlians.
Seriously, as someone who has spent 20+ years living and working away from the city, and half that time abroad, I'm often referred to as a Liverpudlian. Only happens the first time! I was amazed when the Chairman of a large company in Asia called me a Scouser though!
I never have or would class myself as a Liverpudlian, in fairness its a phrase you don't hear much anymore but If its ever said I'm quick to point out I'm an Evertonian not a Liverpudlian.
Scouser, Scally etc dont offend me at all ( unless 'theiving' is put in front!)