Consider yourself "lucky". Getting ordered a muzzle order isn't that bad considering... I'd suggest continuing to follow the muzzle rule but appealing for a specified time limit for future removal.
IMO it doesn't matter the "value" of the dog ANY dog may attack. Monetary value of animals are in the eye of the owner. ANY dog or animal is waaay more valuable than money.
I take my dogs to a walking trail and my dog Shaggy has issues with other dogs. It's an issue I've been working on for a looong time. He's gotten better but definetely NOT a dog to expose to others without supervision and other owner's acknowledgement. He snaps at ANY second.
I have to admit that it IRKS me to no end people allowing their dogs to run off-leash in PUBLIC places. I don't care how well your dog is trained - MINE may NOT be! That is when I have a problem. I am NOW put into a situation where my dog is on a leash but the other dog initiates the contact. NO matter how short/long my leash is, I can NOT control this encounter. That makes me angry because I risk the life of my own dog at my own hands! AND it wasn't my fault!
I hope that puts it into "perspective" of how the other owner may have felt. The fact they have NOT demanded more to be done or that the laws don't extend more makes you a VERY lucky dog owner. I am glad you have made the effort for the additional training and exposure. It is my hope you also realize the danger of not leashing your animal in the future. I say the "muzzle" rule is something you can live with until all training has been completed.