Dog parks often have more bad stories come out of them than good, at least that's how I see it. My take on the idea of socialization tends to lean towards socializing them with PEOPLE. Germans tend to like people more than other dogs anyway.
As to someone kicking my dog, I'd be pretty hot. She had reason, or at least thought she did. There is that. Right now it's a difference of opinion. Leave it at that and go on you (not so)merry way. She was scared for her dog and brutus being a GSD does not help perception matters. Put yourself in her shoes for a moment and be honest with yourself in what reaction you might have had.
Now if someone kicked my dog "just because" orthopedic surgeons would be using said individuals x-rays for years as a case study in major trauma.
Never cook bacon while naked.