I don't really have a problem with the hybrids themselves, but my unease comes from the humans responsible for creating it. More or less, you can't trust people long term to be responsible for these animals given that many reptiles are so long-lived. Stuff happens - medical issues, job transfers, etc - that cause these animals go from owner to owner and each time this happens, the information regarding their origin gets more and more distorted. Eventually you see a post on a message board saying "look what I just got at the pet store, what is it?" and you see where I'm going.
To me, the irresponsibility that many people in the reptile hobby have shown is what makes me very uneasy about hybrids.
Some of the animals themselves are absolutely stunning, though. Aside from the "keeper" issues, I figure if an animal can live a long, healthy life in captivity and do all the normal things that snakes do, I don't see it as a problem.