The update is to answer one, making it explicit that the swords are known fake and you're assuming that the guy won't be able to figure that out, right?

LCPW: You tell him they're fake and he disagrees, insisting that they are real. Now what?

Personally? I'd sell him the swords, assuming there were no other issues. (I might decline to sell them to him on the grounds that he might try to hurt someone with them, but in that case what am I doing selling swords in the first place?)

What I can do is articulate my intuition on this enough to show where the fuzzy line is and why I think something falls beyond the fuzziness.

So do that?

I note that it wouldn't be inaccurate to rephrase my question as a request for you to taboo 'delusion'.