Dog Park Etiquette

Hi everyone. Avery's mom here. I have a question for you about dog park etiquette -both dog and human. I took Avery to the dog park today, which both of us were very excited about. It was our second time there, and our first visit was great. This time there were several doggies waiting to greet us when we got inside the fence. All were well behaved but one, who immediately mounted Avery (who is a neutered male). I pulled the dog off and said "no" and figured maybe that would be it. I was wrong, wrong, wrong. This dog would barely let Avery move a step without mounting him again. I went from thinking, no biggie, just normal dog behavior to becoming annoyed. Finally the owner wandered over and started to pull her dog off. I was trying to get Avery away and to another area of the park, but everywhere we went there was the dog trying to mount him! It was exasperating. Avery is a very gentle and docile guy, and so he just took it at first. Eventually we were able to get away a bit, but inevitably the dog would run up to Ave and try to do it again. The weird thing was that although I saw the dog mount a couple of other dogs, it was not with the same determination (for lack of a better word) that he did with Avery. At first I thought maybe I was overreacting, but then it just got to the point where I was getting pissed off at the dog and even more pissed at the owner, who kept saying "tell him no Avery" as she'd mosey over to retrieve her dog. Assertiveness is definitely not my strong point, and so I wasn't sure exactly how to handle the situation. I just kept moving Avery away when I could, although I really kind of feel like this woman was almost using Avery as a little experiment to see if she could teach her dog "leave it" (obviously without any success). After the umpteenth time of this dog trying to hump him, Avery finally started to get fed up and began growling at him when he got too close. I started to worry that if it kept up that Avery might snap at the dog and then he would be seen as the badly behaved dog at the park.

In my opinion, this woman and her dogs had no business being at the dog park. Both dogs were intact, dominant males and her other one actually got into a fight with another dog (the dogs had grouped into a pack, which I called Avery away from as soon as it formed). What do ya'll think? How would you have handled such a situation? I would really love to hear your advice and opinions! Also, any ideas why this dog would be so determined at mounting Avery when he did not go after the other dogs so repeatedly?

I posted the same question in the General Dog Discussion forum in the Bone Zone on Dogs with Blogs, in case you'd like to add your two cents there rather than post a comment here.