Our Dog park requires a yearly fee and records of the vaccinations of the dogs on file.
Keegan loves to go to the dog park. Yes there have been issues of bigger dogs picking on the little ones but usually the owners act quickly.
I know when Keegan gets to playing rough with other dogs big or small I try to keep her under control and reprimand her. Several times I have been told by the owners "Its ok they (their dog/s) needs to learn." But I don't want to be accused of bringing an uncontrollable dog into the park. Nor do I want Keegan to get hurt or hurt another dog.
I think the lady you have encountered is an idiot and I think by all means she needs to be told it is her fault. Kudos to you.
Once when I was going into our dog park there was a lady coming out with 3 dogs she asked me to stand back b/c 2 of her dogs were dog aggressive. I obliged, and she was very very nice about it. At least she knew not to put my dog in danger. And when I got there she was the only one in the park with her significant other and dogs and then I was the only one left after she left.
I wish you the best of luck dealing with this moronic lady, you are going to need it!! She would try my patience to the point of madness!!!