If there are two sections at a dog park, one large and one small, but the small area doesn't say specifically for small dogs, it just says that it is a smaller area, that does NOT mean only small dogs are allowed. It is NOT against the rules to bring a large dog in that area. If your small dog doesn't like large dogs do NOT get huffy because someone brings a large dog into an area that allows dogs off leash, that does not specify only small dogs allowed. Period.
If your dog is aggrressive, small or large, don't bring it to the dog park. Period.
I haven't had any issues, but people on facebook are all huffy because someone brought a large dog into the smaller fenced section of the dog park that is generally where small dogs go, but is NOT a small dog specific area. Yes, I get it. Small dogs get injured or scared easily, but it's not OK to berate others who are following the rules because your dog has an issue. It's just not OK. argh.