If you are breeding for police, military, leader dogs for the blind, or for working in the fields as a herding dog -- not just a dog to be titled in herding, then you are pretty much breeding for a whim anyway and that includes schutzhund, conformation, obedience, therapy dog, etc. I think a lot less actual damage to the breed itself is done breeding for color than breeding for the desired top line or for a dog that is crazy for the bite sleeve. But it (white) is not to standard.
Well, there are a LOT of things not to standard. 1/2 inch too large is not to standard but people are breeding dogs MUCH larger than that. Lacking in angulation is not to standard either, but people are breeding those dogs too. People breed poor feet, they breed weak backs, they breed things that would make a difference in the dog's ability to do the job.
Color is the last on the list of things to consider when buying a pup, it probably should be last on the list when considering whether or not to breed a dog. Do you breed a dog that is sensitive to storms -- no way. Do you breed a dog that is unstable around children, not on your life. Do you breed a dog that has epilepsy -- no. Do you breed a dog with hair feet? no.
Definitely there is a whole list of things that are so much more important than aesthetics.
Next you want the dog to look like a GSD. Flop ears, happy tail, stubby tail, big white splotch across the chest or on the paws -- they do detract from the look of a shepherd -- moreso than an off-color, even if they do not detract from the dog's working or companion ability.
Which brings us down to color and pattern. I like the saddle pattern black and brown dogs. I do not care for solids, sables, bi-colors, blanket backs, pandas (are they really, really sure?) -- but that is simply a preference, individual taste. I would not try to prevent anyone from breeding these color/patterns. I could really care less about people breeding whites. If I produced a white dog, and sold it, it would be up to the buyer whether or not they wanted to breed the dog. I am not really a fan of the whole limited registration thing people have bought into. If I do not want a dog bred for a reason, I will not provide papers, and even that isn't fool proof.