I honestly believe most line bred fish arent pure species. Take discus for example. They have been line bred for a long time to achieve the colors they exhibit today. All the fish that were bred to create these various color varieties were all discus. However, what is a discus? Right now, we dont even know how many species there are of them, let alone how to tell them apart. Is there only one species of discus? Most likely not. Now, think about the classifications when discus were first being bred. Could they tell what species they were, when we cannot even tell today? I beleive that most line bred fish in the hobby today are that way. Angelfish(Altum, Scalare, Peruvian Altum, etc), Guppies(Guppies and endlers), Swordtails and Platies (Likely hybrids of Swordtails, platies, and possibly other livebearers), Midas/RDs(Self explanatory), Assorted Africans(Who knows what), EBJDs(Not for sure, but who knows), anyways, i think you get the point. In addition, as subspecies become species, fish that at one point would not be hybrids should technically be. What about misidentified fish? In addition, species were once considered to be a group of animals that could interbreed and produce fertile offspring. What is to say that the fish bred to produce so called hybrids arent the same species, if they infact can produce fertile offspring?
So, i think we should face the reality that line bred and hybrid fish are unnatural, and that the only significant difference between them is that most so called "hybrids" were intentially, or at least knowingly, hybridized, whilst line bred fish were at least intended to be the same species.
The question still exists: Should the ACA support hybrids? I don't know. But i feel that so called hybrids and line bred fish should be treated equally, as they are both not natural. If the ACA decides to only support the showing of fish as they would appear in nature, then both should be removed from contests. If they decide to accept one, they should also accept the other. I beleive that currently, line bred fish are in fact allowed at ACA conventions, so in that case, hybrids should be as well, in my opinion, as they are essentially the same, in that they are both not natural and probably not pure.