RE: Why I fight for freedom.
Absolutely.
The non-aggression principle is essentially a concrete and empirical way to determine morality.
Essentially it is derived by the logic:
Man owns himself -> He owns the products of his labor, and that which he trades for.
Because I own my property, and you own your property, and each person owns their property, we have valid claims to do what we want with our respective property. We do not have claims to do what we want with the property of others. Doing something to another's property without their consent is a violation of their property rights, and this is what is immoral. Because it is being done without their consent, it is done through the initiation of force. The non-aggression principle simply integrates these principles, and states that the initiation of force is immoral.