It's so common for people to get involved with dogs, dog walking and dog training because they love dogs. Some of us go far enough to become certified and continue to learn and educate ourselves. Some people decide to walk dogs for others because they love dogs and have always had them in their lives.If you are going to take on the responsibility of walking other people's dogs, it's essential (as far as I am concerned) to learn about dog behaviour, including dog/dog interactions as well as about general health and safetyIt's a beautiful day and I just returned from a walk in the park. It's a warm day, the dogs are hot. I was very unhappy to see an active Border Collie - with a grooming muzzle onFor those of you not familiar with this type of muzzle - it is one commonly used for short term needs (the groomer/vet is cutting nails or dealing with a particularly sensitive area and doesn't want to get bitten). It slides over the dogs muzzle and gives very little leeway for panting, drinking or eating. It holds the dog's mouth ''almost" closed.
Some dogs need a muzzle in public areas, for one reason or another. I believe it's important to know what situations require what type of muzzle. Education does that. A lifelong love of dogs does not.
This situation required a basket muzzle - one that allows the dog to pant and drink.  Without that ability, the dog cannot cool himself down in hot weather. That could be a very dangerous health situation.
If that were my dog and I knew he had to be muzzled, I would want to know my dog walker had the knowledge to choose the proper type of muzzle to prevent unwanted behaviour yet still keep him safe.