Ex-etiquette: I think my son is too young to go online. My ex disagrees.

Q. My son’s father has only come back into our son’s life in the last year. Prior to that he lived in another state. Our son likes to talk to his friends in a social media chat room site, but I do not want him online unmonitored. I believe he is too young and when he does go online, I require him to give me all his passwords so I can monitor his activity. His father allows him to go online at his home without monitoring. I have told his father I do not agree with this, but he says at his age, our son needs his privacy. Our son is 11. What’s good ex-etiquette?