Whoa, what's all this about? You guys don't really think it's okay for a dog to be running around biting horses on a public trail, do you?
I think people who have dogs that will attack a horse in a public riding area should have the dog on a leash (and the law agrees with me.) Besides ... that's just plain manners. It has nothing to do with a person's skill level at riding. Public spaces are for the enjoyment of the entire public, not just a few members.
Dogs that are well-mannered are awesome and welcome around me and my horse anytime. Dogs that attack are not.