They have actually figured out more on the inheritance portion of ME in regards to GSD's. If a dog actively has ME and is bred, it only takes that one parent. If not, then both the sire and dam have to have the gene to pass it to the pups. So if the dogs are still being bred, they continue to pass the gene on and make more carriers.
They thought they had inheritance of DM figured out in GSDs too, but there sure seems to be a lot of evidence to the contrary coming out, and I think it would be very detrimental to throw out all the dogs who might have 'bad genes' especially when these DNA marker tests are apparently not as cut and dried as some people think.
And if the tests are accurate, then there is the option of utilizing them to prevent producing dogs who are affected without having to eliminate all carriers from breeding and potentially narrow the gene pool severely in doing so.
Every dog has bad genes and will pass them on. Eliminate every dog without perfect genes from the genepool, and there will be no more dogs. Period. Breeders have to gather as much info as possible and use it judiciously to minimize risk, but no matter how much we all may wish things were different, there is no way to eliminate risk.
It's interesting that there are breeding programs out there that overfocused on specific health problems, and did in fact all but completely eliminate those health problems from their lines, only to have new ones pop up in much greater frequency than exists in the general GSD population. It's always balance, and as the saying goes "when you breed something in, you breed something else out" and vice versa.
Why is it different with ME than it is with hip displaysia? If a dog has severe hip displaysia then the dog would not (or at least should not) be bred. Wouldn't that be considered taking dogs out of the gene pool as well?
It isn't. But originally you were talking about a dog who had produced a pup with MegaE. Now you're talking about a dog who HAS severe dysplasia. That IS different.
The affected dog should not be bred. A dog who is related to the affected dog, even if a littermate or parent, IMO should not automatically be thrown out on that alone. Goodness, if we eliminated every dog who produced or had a littermate with HD from breeding, we really wouldn't have anymore GSDs. The same common sense, look at the big picture approach needs to apply to all traits.
And honestly, one area where MegaE is preferable to other health problems is that it is becomes apparent when pups are very young. Usually as soon as they start solid food. So it should never be a surprise to the new owner. The breeder ought to be able to identify it well before pups are going home, determine the severity and then either euthanize or place the pup in a home appropriately based on that information.