I'm sorry your young dog had this experience. It is just more proof that the world is full of idiots!
At a holiday get-together, one of the guests pinned my dog to the floor and blew on her face. She struggled to escape, which he found amusing, so he kept doing it. Finally, she swung her muzzle crossways across his face, hitting him with her teeth. (I saw only the end of this.) Though she was not closing her mouth, this jerk's girlfriend went around telling everyone "That dog bit Gary in the face!" Both these people were in graduate school, specializing in animal behavior (ethology)!
Since Goku has had this encounter, I'd suggest a deliberate program of socialization. Have as many strangers as possible meet and pat her (after proper approach!) to dilute this bad experience. One of my friends who trains search and rescue dogs takes her pups everywhere to give them lots of experience. One had a weird fear of kids wearing winter hats, so my friend worked on getting her lots of positive experiences with children.
Best of luck!