Loki: Dog of Mischief

There are many different types of muzzles, but most are muzzles that should allow the dog to pant and not inhibit them in anyway (other than being able to bite). 

The types of muzzles that do not allow a dog to open their mouths are typically used at vets or grooming salons and not left on for long periods of time. These types should not be used to go on walks because they prevent panting which can then lead to overheating.

It’s important to know the difference between a muzzle and a gentle leader, or head collar. 

This is not a muzzle, it is a head collar similar to what you would see on a horse.

“Properly trained” typically refers to obedience. Dog aggression, whether it is towards other dogs, children, people, or animals, isn’t something that is an easy fix. It can root from many different sources like fear, frustration, pain, possessiveness, protectiveness, predatory, gender, and more. 

If someone has a muzzle on their dog in public, it is for the safety of the dog, and others. The owner is not only being responsible, but some cities have laws that require muzzles, and some dogs (especially greyhound like you mentioned) are newly adopted and might be fearful of their new surroundings. So, the new owner is just taking precaution.

It’s also important to note that most people are actively working on their dog’s problems. So while they might be working very closely with a dog behaviorist at home, they may still feel more comfortable muzzling their dog while on a walk until training is 100% complete. And some dogs may never get over their aggression, depending on where it is rooted from, aggression is something that can be genetic.