I go to the dog park often and I've seen 7 adult gsds and 6 of them were dog aggressive. Once 2 gsds saw my pup they just wanted to kill him. They made this loud, aggressive sounding sort of whining sound because their owners would not let them come close to my pup. It was a family of 2 gsds and they both were wearing muzzles. Another time a gsd attacked my pup, I'm not sure why and there were 3 other times where I 3 gsd owners told me not to take my pup near theirs. Only one gsd i've seen so far have been dog friendly and he was only 11 months. I have my own gsd pup, i dont want him to be like the rest of them. Now my parents think he might become dog aggressive too.