Even when I was training my dog, I didn't realize how much he would actually help me. Now that he's working...I'm not entirely sure how I functioned without him.
Adog misbehaving should be kicked out. Period. EVEN IF A DOG IS A SERVICE DOG, if it's misbehaving, it can be kicked out, SHOULD be kicked out, and kicking them out is the right, legal thing to do. There are questions that can be asked of a service dog handler to determine whether the dog is an SD or not. If it comes down to going to court, YES, the handler does have to prove their disability and prove their dog is an SD (typically via training logs and behavior).
Also, allowing dogs everywhere becomes a health issue (in grocery stores, restaurants). Service dogs get a "pass" because they're considered "durable medical equipment" and are needed by their handler. Also, they're supposed to be impeccably groomed. if a service dog s dirty, that is a valid reason to kick them out. There are also people who are afraid of or allergic to dogs that have every right to go shopping. Again, service dogs are well-groomed, not in the store very long, well-behaved, and any good service dog handler will respect the space of someone who is allergic or afraid.
Contrary to what most people here seem to think, have a dog in public every day, every time you go somewhere isn't all sunshine and roses. It takes time to get the dog ready to go. People stop to ask questions. People try to pet your dog without asking. Children run up to your dog without asking and you have to body block to keep them away. People try to stuff food in your dog's face, step on feet and tails, hit them with shopping carts, drop things on them. Not to mention it is VERY stressful on the dog, and most dogs, temperamentally, cannot handle it and it's not kind or humane to make them try to handle it. Then you have the PETA/AR nuts that will try to steal/injure/kill your dog to free it from "slavery." Why anyone would want to deal with that hassle. every. single. time. they go somewhere without actually NEEDING the dog's assistance is beyond me.
Now, I do think that canine ESAs, though not task-trained, should be granted access under the same behavior stipulations as SDs. some states allow that already, but not all (federal law specifically prohibits it, but states are free to allow them under state law). I can understand that a dog just there can be helpful to some people with certain disabilities, and I also think most of these dogs would end up task trained in the end anyway.
If a dog is well behaved and acting appropriately I don't care where they are at all. and on the other hand, i don't care if the dog is an actual service dog, if it's not acting like it should, GTFO.