It's on the owner to train and raise the dog, Also it's a hefty fine for not picking up after the dog and or having it off leash in areas. if the park allows dogs and their owner is a lazy peice thats not the dogs fault.
I will bring my dog to certian courses and not to those that arent dog friendly, I feel the same way that you do about the untrained dogs that run a muck and ruin discs and courses. But it's not their fault.. IMO it falls on the owner. Blame them and report them if needs be.