There are grammar errors here and there, but otherwise a solid essay.
The only contradiction I found in the essay was calling aggressive companies "defense" agencies. At the point of aggression and/or attack, it would seem to me that they cease to be a "defensive" entity and simply just a paid aggressor. Defense implies impeding and/or neutralizing an attacker; defense does not imply aggression against someone else. If a company was attacking people, it wouldn't be in the business of defense. I thought I'd just mention that bit.
I think a great example of private defense would be body guards. Why would a body guard initiate force against somebody else, especially someone who is non-violent and unthreatening? Why would a body guard stab you in the back? You pay a body guard to protect you; your well-being is their well-being.