They don't have to be next to a dog to have a reaction from it, or for the dog to find opportunity or accidently contaminate food and open liquid. Most fresh food related establishments limit to service dogs while inside and pets are allowed outside only for a bunch of good reasons. EVERY paying customer deserves to avoid having a major issue because someone insisted on bringing an unnecessary animal inside.

Outside, you should have free reign.

The other issue, you're spot on. If there isn't a true and intentional transgression by a service person, people shouldn't complain. And even then they should take the high road as much as they can.