I honestly don't think that there is or even should be a dramatic back story on why he doesn't like Kantoans. From my perspective, it's not Kanto he's concerned about, it's anyone from a no-name, "hick" town...and I thought that that would get expanded on, but it was left quite shallowly. He could have been presented with other region trainers that showed him exactly how he can't judge people based on where they were from...SOMETHING. But it just seemed like a quick insult just for the hell of it.
Flashback with Alder got me squeeing, and I like his character design. He's pretty :3 But, yeah...neglected and two dimensional v_v;
Well, as you see, I posted in there anyways XD I'm going to try to be an active shipper again, but it'll probably fail after a few posts XD