Stories like this really make me scratch my head. I've actually seen something like this happen in person and it was extremely awkward. ML Leigh trains service dogs and was at a mall with some of the dogs that she is training.
A woman and her daughter came up and asked if they could pet the service dogs. One of the trainers told the woman no. Of course, sometimes we see a dog in public and in some cases want to pet them, but these service dogs are working and if you treat them like a normal dog, it could throw them off and mess up their job they were trained to do.
Service dogs wears vests that show they are working and some have signs that say, “do not pet” just like the dogs in the video. The woman who asked to pet the dogs wasn't thrilled when she was told no and confronted by the trainers and things escalated after that!