I commented on this thread on Twitter. Yorkshire Tea were nothing more than a prop used in a very transparent nod to the north. I took it for what it was. That said, they wouldn't pull stuff like this if it wasn't effective in some way and I think some of the 'outrage' comes from people that are worried about others that don't see through it.
I also think that Yorkshire Tea have been clever with that thread in order to spin the narrative in their favour, although it should never have gone against them. I don't believe the team running the socials will have been feeling exactly as described in the tweets but maybe I'm a cynic.