Yes, I know, many dog owners balk at using a muzzle because they envision their dog looking like Hannibal Lecter. Here is how I look at it.
I think most dogs should be worked with to accept and like wearing a muzzle, starting with young puppies. This is preparation for an unknown future.
Imagine it is now 5 years in the future, your dog is severely injured and needs to be handled to get to the vet or to be treated by the vet. If your dog is already muzzle conditioned, the quicker the medical team can get to work on your dog, often without having to sedate your dog.
Or let’s look at the same scenario, but your dog is now 12 years old, and there is a high risk that your dog might die if sedated. If your dog would accept the muzzle, the possibly a local anesthetic could be used, and your dog survives.
Let’s say one day your dog is getting in fights with another dog in the home, or you are introducing a new pet (dog or cat) into the home, but you want to lower the risk that a person or dog is injured if a fight breaks out. You could do the introduction safely if your dog accepts the muzzle. For resident dogs, you can better do the remedial work if the dogs already are accepting of wearing muzzles. That’s better than having to take a dog to the ER, or worse. In some (not all) cases, I will recommend that the dogs which are fighting in the home wear muzzles when around one another until the dogs can be safely managed together. Sometimes dogs can peaceably live together without ever being muzzled: you avoid the triggers of the past fights and just do some more control work to avoid confrontations. In other cases, the muzzles are used until sufficient control is obtained. In some cases, the only way to safely have some dogs near others is to have them all wear muzzles for the rest of their lives. Better that than having to rehome dogs that might have been able to live around one another with some additional safety precautions.
Muzzles aren’t evil any more than wearing a collar or a vest.
You can’t just put a muzzle on a stressed or injured dog. They will fight it and pull it off. In an emergency, it is too late to try.
I think muzzle training is an essential puppy training goal. I am always thinking long term, knowing what might happen to any dog years in the future.
Plan accordingly.