I think this has more to do with your situation than the moral decision. Why are those dogs homeless in the first place? In a lot of cases, their people chose them for the wrong reason and couldn't handle the commitment of a GSD. I don't recommend a rescue for a first time GSD owner. I think the first time owner needs to grow with the dog.
I agree with you on the first bit, and was actually coming to say pretty much the same thing, but the second part I disagree a bit. I think you absolutely can have a rescue GSD for your first GSD, but it REALLY needs to be evaluated by a rescue group that is GSD breed specific. Meaning, they are absolute pros at evaluating temperament and getting the right dog in the right home. Just like a good, reputable breeder will help evaluate the right puppy for the situation, a good, reputable rescue will do the same. Moreover, by adopting an adult dog with known temperament, you can even get a dog that already has some obedience and housebreaking under its belt, and you can be past the difficulties of puppy-hood and adolescence. If you're unsure of your handling skills and get a puppy from a breeder, you could possibly BE one of those people that didn't know what they were getting in to, you know what I mean?
At any rate, this whole thing is the same issue I struggled with for years before settling on what I felt was right for us! What it really boiled down to was our goals for our dog. I'm really looking forward to getting involved with SchH, and I want a dog with an absolute rock solid temperament because I have a toddler. It's a really fine balance finding what I want in a rescue (not that I haven't been looking, just in case!) so a breeder just really feels like the right fit. I also have known tons of shepherds with breed specific issues that I really would like to avoid, so going to a breeder that tests and tracks for all those things in their lines will put me at the best possible advantage with that.
So what you really need to do is take a good, objective look at your life, situation, handling skills, etc. Are you looking for just a good dog to fit in with your family, or do you have specific goals in mind? Do you feel comfortable raising a puppy, or would you feel better off with an adult with a known temperament? Do you have a breed specific rescue in your area that you would feel comfortable adopting from?
Good luck with your search! You'll make the right decision in the end.