I'm sorry this happened and that your dog is not well.
Like not allowing for authorities/businesses to demand certification to prove a dog is a service dog.
I don't think it's unreasonable for people to provide proof that a dog is actually a service dog because too many people are 'faking' it these days.
Think of it this way, when people can easily get in anywhere with a dog that is not really a service dog, the dog misbehaves, it actually makes legitimate service dogs look bad.
I talked with a lady at petsmart last summer, she was bragging on how she took her GSD into the Atlanta Aquarium, told everyone it was a service dog even though it is not.
You also have to look at it from the business owners point of view too, they can't have, for instance, fake service dogs coming into their store and damaging merchandise or disrupting other customers.
We have to be fair to everyone