Ew, This Is Gross
There’s something we want you to notice from this story. Notice how the OP used the term “man” to describe the person in question. They didn’t use the word “child.” This would indicate that the person who took a sip of soup from the serving ladle, spit it back onto the ladle, and returned the ladle back into the serving bowl was old enough to know about germs.
Sadly, that’s where the OP stopped telling the story. He didn’t make any mention about how the entire restaurant got up and beat the guy to a pulp for contaminating an entire serving bowl in one of the most disgusting ways possible.