I really don't care what word to which anyone is referring.
If I wanted to live in the type of world this country is becoming, I would have been born in Communist Russia.
Acting in a professional manner is an obvious must for an umpire. HOWEVER, that doesn't mean we are not allowed to speak and use words meant to communicate an idea, meaning or intention. The word "muzzle" was an appropriate word to use in the scenario described. Of course, if anyone would bother using a dictionary, that would be a no brainer.
From Merriam-Webster: Main Entry: 1muz·zle 
Pronunciation: \ˈmə-zəl\ Function: noun Etymology: Middle English mosel, from Middle French musel, from Old French *mus mouth of an animal, from Medieval Latin musus Date: 15th century 1: the projecting jaws and nose of an animal : snout
2 a: a fastening or covering for the mouth of an animal used to prevent eating or biting
b: something (as censorship) that restrains normal expression
3: the open end of an implement ; especially : the discharging end of a weapon
But in our present society, people think the worse and it makes them feel superior by finding fault in others instead of examing their own reflection.