I dont know the history here or really care, it always looks bad for everyone when the drama starts. Regardless Ill always love the Holy Diver recording and The Riverdogs. Even if someone wants to view it as Dio gave Campbell the chance, Campbell stepped up to the plate and delivered, I always liked his guitar work. I havent kept up on Def Leppard since Hysteria.
If anything, Im willing to bet Dio started sparking because he just didnt want to hear someone start talking about someone he no longer plays with. In the end you can here him say something like Im out of here in a few seconds. So the dude sparked him more than anything. He probably felt like telling the guy he was a fucking asshole for bringing it up but released on Campbell cause it was easier. He was signing autographs and suddenly was put on the spot. Like when you take a girl out and all she talks about is her last boyfriend.