Sorry that the park ranger spoiled your day like that. We are very fortunate. Our parks are very pet friendly and even have "Paw Playgrounds" just for the dogs. Even just walking around or having a picnic at one of the shelters, dogs are more than welcome (on leash and well behaved, of course). As long as the park rules state that dogs are aloud and you weren't violating any of the rules I'd definitely be complaining.