A Legal, Perhaps, Ethical Gedanken

Disclaimer: I do not believe that the law and ethical behavior are always in alignment with each other.

Now, my thought experiment:

First, a neighbor implies to you that he would have preferred that you had never moved in next door by saying, “I wish that you were removed from the pages of time.”

Second, he purchases a gun.

Next, you have heard that he is looking to purchase a rocket propelled grenade launcher.

Assume that these are legal to possess. In fact, you have these weapons as well.

Are you within your rights to fire your weapons first? If so, why?