Ask Lemmy

If you have the right relationship for it, ask him about the porn he watches, his banking details and how much money he's got in his account, and tell him you'll go buy a billboard to put those on.

Those usually get people quite quickly, but they're also kind of "gotcha!" moments, and people will generally not respond well to them.

If you want a more structured argument, I think you'll need to reframe the issue. As I read your comment (I'm almost certainly missing huge amounts of context that could change this answer drastically) your father's argument is "privacy is bad because it is only used for bad things" and you're actually arguing back "privacy is good because I want to be left alone". But your dad thinks that you shouldn't be left alone, because being left alone means you're doing something bad.

So, don't argue why privacy is good, you need to argue why privacy isn't bad. Find some examples of things he likes that only happened because of privacy. Try to avoid things like revolutions, resistance movements or stuff like that, because it will only reaffirm his view that privacy means you're doing something bad/anti establishment.

This is where the aforementioned porn/finances comes in, since those are usually things people want to keep private, without having negatives attached (depends a bit with porn on morals). Any guilty pleasures that come into mind would also be useful for this.

Also, make the consequences of no privacy more personal. Government whatever, but what about Janet two doors down? What about his boss? What about his parents?

In the end I'd say it's all about the framing of why privacy matters in the first place. Establish a minimum need for privacy, then expand from there. Hope this helps you (or someone else)!