There are almost as many definitions of what constitutes a species as there are people attempting to define it. It all depends on the perspective from which you are trying to make the classification.
As for the genetic "purity" of species, I kind of disagree with you, Abrahm, but not in your stance against hybridization. Evolution and adaptation requires diversity, without it a population cannot change nor can the individual cope with changes in the environment. The "purer" a species is, the more easily it falls to disease, climate variability, niche disruption, etc.
However, evolution has worked for many millions of years to make these animals better able to meet the challenges of their respective environments. Contrary to popular belief, this has not occurred through just random chance, either. There are very significant 'reasons' to how and why these organisms are the way they are, and anthropomorphic hybridization throws that all right out the window. The way I see it, you are entirely right in that hybridization is of no practical use except to produce "designer pets" to fuel greedy interests. Maybe I'm being slightly arrogant, but when one is in favour of hybridizing, I think they have no respect for the animal in and of itself, of the wonder and culmination of fantastic forces it took to bring the organism into existence, and reduces it all to little more than a status symbol. Way too many people in the herpetocultural trade have gotten into this fad of hybridizing, too quick to ask "can it be done" without ever even contemplating "if it should be done".
I'm against it, especially in the uncontrolled manner that so many hobbyists pursue it. If any one of those hybridized animals ever makes it back into the natural gene pool and it successfully reproduces, it will not only completely disrupt the genetic distinctiveness of that population, but potentially unravel all that evolution has accomplished over the millenia. It is a foolish path to follow, and it would be most responsible to not take the first step down that particular path.