I always get that question too. Levi is registered as a White Shepherd through the UKC, and as a white GSD in the AKC. I used to say that he is a white shepherd, but that usually results in blank stares, so now I say that he's a white German shepherd. Usually then, I get nods and smiles. Though it seems there is still a stigma against white shepherds, especially among some GSD fanciers, no one has been condescending or rude to me or Levi in person. If it comes down to it, I am perfectly willing to consider Levi a different breed if that makes folks happy. He is both very similar to and somewhat different than other "traditional" GSDs I have known. He's a wonderful dog, and I am grateful that there are good and responsible white shepherd breeders out there.
(To be fair, a GSD of any color other than black-and-tan is likely to confuse the general public. When I had a sable working line GSD, one of our veterinary offices listed him as a GSD-mix in their records. Now, I don't care if the general public thinks I have a mix. I love mixes. But I would like to think that the veterinary staff would be experienced enough to know that GSDs come in different colors.)