You should respect her wishes and get your dog away from hers. You really should be "stalking your boy the entire duration" if you can't control him with your voice and call him off of dogs/tell him to leave certain dogs alone.
Sure, the lady might be overreacting, but she has a greyhound. I would never allow my boy to play with a greyhound because his "normal" play would crush one and likely break it in half. Does that mean greyhounds probably shouldn't be at the park? Probably...but there are hundreds of people that believe GSD shouldn't be at the park because they do tend to play rougher. If the lady had tried to remove her dog from your dog, and your dog kept following/trying to play with her dog...you should've called your dog away as she was clearly trying to avoid your dog. After trying to get away from your dog, and you not stepping in, she finally decided to let you know that you should call your dog off.
There is also the chance that she knows her dog doesn't appreciate the way your dog is trying to initiate play, and is actually protecting YOUR dog from something bad. If he's a puppy...that greyhound might try to correct him inappropriately and then you'd be on here writing "A greyhound attacked my puppy at the dog park."
IMO...if you can't recall your dog or tell him to leave a dog alone with just your voice, you should never be farther than a 5 second sprint from your dog. Dogs can go from play to fight in the matter of seconds, and even if you're not worried about YOUR dog starting the fight, you should be worried about your dog being at the bottom of one. I don't allow my dog to play when both dogs are standing still, or he's starting to mouth at the other dog's back. I like a nice game of chase, but once they stop and start staring/biting...things can only escalate. Generally at that point I will call my dog off and walk somewhere else.
Always keep in mind that you own the "dangerous breed." Your shepherd will get blamed for EVERYTHING unless there's a pitbull running around.
As far as "correcting" or yelling "no"? Don't yell no...just redirect him. Call him to you, and then praise for coming to you. You're right...correcting him while he's "playing" can cause a miscommunication...so just redirect.
Last edited by martemchik; 12-23-2013 at 02:58 PM.