I don't remember where I heard it, but I really like this definition of privacy. It's a defense against bad laws and there are quite a few of those, including child porn and child abuse laws that actually lead to prosecution of adolescents (sending nudes to each other) and loss of access to medical information for kids (anyone tried to search for "12yo penis" images?).
People may use privacy as an excuse to hide their crimes, but criminals are minority and lawful citizens will be exposed to criminals and police states if privacy shield no longer exists. As for child abuse, when we have to seek for evidence, the crime has already happened. Solving it is important, but what is more important than that? Prevention.
not even all police coercion is legal; when the police disappeared tens of thousands of people here during the last dictatorship, the police were breaking the law, and in some cases the disappeared were not
also, privacy can protect people from repercussions from activities that are legal at one time but prohibited later, perhaps after a change of government, such as celebrating passover