Q. Is it all right to use violence against people who belong to NAP-violating organizations (e.g., Nazis)?
A. It may seem reasonable to think that if person A belongs to, or agrees with, an organization that propounds notions contrary to the NAP, it is therefore acceptable for anyone else to use violence against person A. After all, their organization wouldn’t have any compunctions against using violence against you.
Let’s just look at this practically, forgetting for the moment the moral issue of pre-emptive NAP violation.
Virtually everyone in society belongs to one of these organizations, or at least agrees with NAP violations propounded by one of these organizations. These organizations are called “political parties”.
If you have the view that anyone who agrees with one of these organizations’ NAP-violative policies is “fair game” for “defensive” violence, you have just turned almost everyone in society into your mortal enemy.
This is not a very good approach to reforming society in a positive way, so the answer is “No”.
Q. Is trespass a NAP violation?
A. Yes, because trespass forcibly prevents you from using your own possessions as you wish.
Q. Does trespass authorize lethal force against the trespasser?
A. Not unless that is an appropriate level of force. The requirement to use only an appropriate level of force applies in this case as in all others.