The Jacks hate the Valleys because they are bitter they don't have a decent Valleys following. I hear over and over again the Jacks saying that Cardiff have biggers crowds because the catchment area includes the Valleys.
I live in Trecynon. As the bird flies, its 20miles to Cardiff and 21miles to Jackland. Aberdare is bang in the middle. They turn on the Valleys because given the choice, most Valleys people back City, not the gypos.
Simples. They're bitter that the Valleys don't back them. And without sounding snobbish, but Valleys people have more in common with Swansea than Cardiff. Valleys people are a bit common, compared to Jacks who are very very very very common.