In the world of dreams the rules of reality do not necessarily apply. Each dream is unique and it's a direct link to the soul and spirit. Psychology provides its own theories on what dreams mean, but so did tradition and the study of dreams for thousands of years before any relevant science had developed.
Dream Meanings - Muzzle
If you dream that a friend puts a muzzle on you, you will receive the help and protection of a friend to get out of a difficult situation. If a stranger muzzles you, then something problematic will be said to you.