Dog Growls and Snaps When Taking Off Its Sweater?

I have a Yorkie/Shih Tzu mix. He likes wearing sweaters and gives me no issues putting them on. But as soon as I try to take it off, he freaks out. He starts growling and trying to bite which he never does at any other time. This is completely out of character for him. Does anyone know why? Or does anyone else's dog do this?