Why do law-abiding citizens need strong security?

You don't need to lock your front door unless you're a thief.

It's the same idea in all relevant respects.

Each person needs to take reasonable measures to protect himself and his property from those who would harm him or his property, in accordance with his best judgment of the risks.

You buy a lock and lock your front door if you live in a city, in close proximity to hundreds of thousands of others. There is a reason for that. And it's the same reason why you lock your Internet front door.

My first thought is to ask, “Do you have anything valuable that you don’t want someone else to have?”

If the answer is Yes then follow up with “Are you doing anything to protect it?”

From there you can suggest ways to protect what is valuable (do threat modeling, attack modeling, etc.).

As the Miranda Rights say: "anything you say can and will be used against you in a court of law". Right after the police finish giving you the Miranda rights, they then say "but if you are innocent, why don't you talk to us?". This leads to many people getting convicted of crimes because it is indeed used against them in a court of law. This is a great video on YouTube that explains in detail why you should never talk to cops, especially if you are innocent: http://www.youtube.com/watch?v=6wXkI4t7nuc

One of the more common crimes in America is "conspiracy". Hackers frequently don't get convicted of the actual hacking activity, but of conspiracy. That's because the police have chat logs of them discussing the attacks. Even if you aren't really involved, have no intention of participating in the hacking attack, and even tried to discourage your friends from doing it, you can get convicted of "conspiracy".