Agreed. That time they really do deserve the scolding they get.

I think you're exaggerating a bit there. His way of acting towards his son is normal enough, a father proud of his son, in a way not unlike the hero worship Cedric gets from the other Hufflepuffs for bringing them some glory which they usually don't get much. And after all, he wasn't there during that Quidditch game, even if Cedric has told him about the Dementors it would be hard for him to fully appreciate all the subtleties of the matter. It's silly to talk of him having defeated Harry Potter as if Harry Potter has to be a Quidditch god just because he happens to be the Boy Who Lived, but understandable enough.

I think we've all witnessed situations like that, or been in such conversations - parents boasting about their child in the presence of the child, who stands there feeling awkward and fruitlessly tries to nuance things a bit. It hardly means those parents are comparable to the Dursleys.