# Like one who takes hold of the ears of a dog is a passerby who becomes angry at a dispute that is not his own

"A passerby who becomes angry at some other people's dispute is like a person who grabs hold of a dog's ears"

# Like one who takes hold of the ears of a dog

"Like a person who grabs a dog's ears and is bitten by the dog" 

# is a passerby who becomes angry at a dispute that is not his own

The passerby will start arguing, and the people who were fighting will get angry with him and hurt him.