Would you care to try and make an argument that just "anyone" owning arms is a threat to you? I had some idiot try that on me once. "Why do you all need guns if no one is supposed to initiate force?" Because some of you aren't adult enough to just behave on your own.
And no, non-initiation extends to fraud and theft. If someone steals your property, you are within your moral Rights to re-assert your claim of ownership by stealing it back.
I was merely taking Ms. Rand at her word: "...no man may initiate the use of physical force against others." It's an absolute statement, and you likewise were being absolute: "there is nothing 'relative' about the non-initation principle."
Situations like these do not arise apropos of nothing else. And no, the armed man just POINTING a gun in your direction is justification enough. The threat of force has been initiated.
Here we see a subtle but important shift: you've slid your standard from the actual initiation of force, to the threat of initiation of force; and you've also tacitly acknowledged my point about the subjective principle of "reasonable cause." Your standard here is explicitly relative, since it is based on your (necessarily subjective) assessment of whether or not the man represents an actual threat.
Thus we see that there is, in fact, something "relative" about the non-initiation principle.