Whatever your definition of "responsible breeder" is (it really seems as though that phrase has become so cliche here), certainly you'd agree that a responsible breeder DOES breed for solid nerves. So the better question in my book is why are so many people getting such poorly bred dogs?
I haven't read the thread you mentioned, but in another thread I read someone say that breeders should be so much more particular about what they breed. I really think that we have to just flip that mentality- BUYERS need to be so much more particular about what they buy. There are plenty of good breeders out there in all GSD lines. But when you buy from a crappy breeder, your chances of getting a great, stable dog are highly diminished.
C-ATCH Pimg - DOB: 2/06, RATO, UJJ (x2), DJA, HIT, CA, CGC, High in Games, Reserve High in Standard- CPE Nationals 2014
RATCHX High Jinks vom Neuanfang - DOB 9/12 (Gotchya Day: 1/23/2013) CA, agility superstar in training