I understand the empathy and sympathy being expressed in this thread but I think it's a little misguided.
Having been the breeder of 13 pairs of these fish, the problem I see is that the fish may have posed too much of a job for the owner to maintain properly which was why they were left at the LFS. I used to breed my Oscars in custom made 50 gal tanks. 2 fish, 50 gals of water. The only "problem" I had was that due to the size of my fish, the "bioload" (a.k.a. Fish POOP!) was such that I needed to do water changes much more frequently than in my other breeder's tanks. For someone with so many fish in that size tank, this might have just been too much work for them. Don't forget about the cost of feeding that many Oscars. It can raise a nice hefty food tab too.
As for the dents and dings on the fish, a breeding pair of Oscars often do some serious damage to thier mates. Most of my pairs would not have been "aquarium grade" fish for anyone wanting to have a nice big fish for display. But after the fightin', the lovin' started and eggs were laid. So, even if these fish were in a 1000 gal tank and paired off, they still would have had a number of dings and dents so you really can't blame the tank size for the condition of these fish. It's an unknown at this point as to why.
I agree with you all that not enough info is either given by the stores who sell these fish or gotten by the hobbyist who want these fish. There's enough blame to go around here for sure. So, if you want to raise these wonderful fish without doing a lot of work, keep them in bigger volumes of water BUT, if someone is willing to put in the effort, don't admonish them for keeping the fish in a "smaller tank" (within reason of course) because they can be kept and well cared for this way. I have produced too many babies that prove this.
Something else to consider, I've seen these fish in the wild (canals in S. FL) and they really don't use a lot of space. I'd see a single fish in a spot and see it there for days on end, not swimming far from his hole. I've also seen pairs with fry in the space equivilent to a standard 75 gal tank. So the justification for these huge tanks for Oscars, I believe, is more human based than fish based. I refer you back to the water management part of my post
I hope I have shed some new light on the situation. Thanks for listening.