I've actually never kept discus...but I think that they're beautiful fish. And getting them to breed is an accomplishment.
Whether they're hybrids or not is a subject of some controversy. Certainly at the time that fancy discus were developed, discus were described as multiple species... and it's not as if anyone working to develop fancy ones put maintaining species / variant "purity" ahead of developing the fish with the aesthetics that they desire (color, shape, etc.).
As frequently happens, there's now disagreement about the species status of the various discus types. Scientiests don't agree.
Whether retroactive un-hybridization (i.e. if the discus in fancy discus varieties are now technically a single species vs. 3-4 different species... as they were when they were developed) makes them OK with those who are "against" hybrids like flowerhorns and fancy peacock types, seems like a rationalization to me.
For the record, I'm for whatever fish - especially cichlids - that make you happy and want to participate in the hobby
Matt