I don’t have “something to hide”, it’s just none of your business
If you have nothing to hide you have nothing to fear
But privacy isn’t about hiding anything. Protecting privacy is about protecting the right for you to say “this is none of your business”, and to have that respected.
If you keep a journal or diary, what you write there is none of anyone’s business. It’s private. You may choose to share part or all of it with some people, but you expect to control what you share and with whom. If someone read your journal without your permission, you would rightfully be angry. If they then shared what they read with others (again, without your permission), you would rightfully be livid. They have violated your privacy.
Likewise, what you choose to look at online isn’t secret, but it’s not anyone’s business either. It’s private. You may choose to share bits of it with some people, but you should expect to control what you share and with whom. When Facebook or Google decides to examine, retain, and share that information about you without getting your permission first, it is not really any different than having read and shared your diary.
In other words, the right to privacy is a right of control, not of secrecy.