I've always found the pro-privacy argument "well let me see your email than" to be weak. But when someone responds to this "here, no problem" this indicates exactly what the problem is: Apathy.

A lack of privacy induces apathy. This is exactly what your friend responded from and acted upon. The better argument to start with, and one that counters apathy, is: I do not value privacy because I have many things to hide but rather because I have many things I value.