I think your logic is a little bit overcomplex. I understand what you are saying - nobody wants to kill, people want to feel safe. They buy guns to feel safe, not to kill. I believe that to be true.
At the same time, guns are designed to kill, not to satisfy your need of safety.
There are many other items that work in a similar manner - airbags are designed to save you in an accident, but you want them in your car to feel safer. Burgler alarms are designed to react when someone is breaking into your house, but you install them to reduce the risk that someone will even try, contracts are designed to cover your ass in case of a court case, but they are signed in hope that it makes court case less likely etc.
But coming back to wepons, they are designed to kill. You can argue that fake guns are designed to scare attackers, but real guns are designed to kill. Their parameters, their tests, their ads, their designs, are all focus on precision of shooting, targeting, and efficency of the bullet to penetrate the target. They are designed to be a good tool for killing.
Tor is designed to be a good tool for privacy and anonimity.
You can test it using a simple mental experiment - if the needs of pedophiles and people needing anonimity diverged and became incompatible, I honestly believe that Tor would be developed to fulfill the needs of the latter group.
If the need of people looking to feel safe would diverge from the efficency of a weapon in killing, then I honestly believe that the weapon manufacturers would keep designing weapons to be efficient in killing.
> but I don't know anybody that regularly uses tor or pgp for emails and such.
That's a fallacy here. You may not know people who use it, because you may, guessing here, not spend time with people who have a reason to be afraid of their governments. You may not be part of the wikileaks movement. You may not know journalists who track mafia in Italy or Russia. Those are just examples.
And, because I work on multiple open source projects, I definitely know many people using PGP on daily basis.
> if you say the purpose of a handgun is to kill a human, I wonder what percentage of their regular use for that purpose is by criminals, it has to be pretty high, much higher than non-criminal use.
I guess you are right. :)
But I'm not sure how it relates to the topic of authors intentions.