See even if a legit trained service dog is having a meltdown and causing a disturbance, just like if a human was causing a disturbance, the restaurant is entirely within their rights to eject the dog and the owner. This is just restaurant management not wanting to deal with it and being more comfortable making all of their customers unhappy than having to have a confrontation.
And knowing a number of people with actual service dogs, they'd all be the first to make a quick exit if their dog was doing anything even remotely disturbing.