OK, maybe it is just because DH and I both have many relatives that hunt (not our favorite thing in the world but they do actually USE the meat and animal products, and seem happier to have the food than to have killed an animal, so we can live with it), but I think that I would allow a dissassembled and locked gun into my attic.
I think that if I felt so strongly about the matter that I wouldn't allow such a situation, where the safety was absolutely maximized, then I wouldn't let this man visit, either. It sounds far more dangerous for it to be locked in his car, assembled, just a key-turn away from disaster, than for it to be dissassembled and hidden, KWIM?
Then again, none of my relatives own pistols, they all own rifles, and they wouldn't ever take them on a family visit. It kind of freaks me out, unless this guy is in law enforcement anyway. I mean, it is one thing to have hunting rifles and use them for hunting, and quite entirely another to have a pistol you carry - for what? To shoot someone? I don't want someone who would carry a pistol "in case they needed to shoot someone" in my house, because that's just a wrong kind of attitude IMO.
But whatever else is going on here, it is YOUR house and if you are uncomfortable with the gun, that is YOUR call. If he knew in advance how you felt and still brought the gun, knowing that this situation was possible, then he totally shouldn't have pushed the issue and should have taken care of the matter himself. Whether he knew about it or not, he should have been responsible for finding somewhere else for it or for himself. If you say no guns, then the rule is no guns. It is your house and you have that right, and although I would have grudgingly allowed a locked dissassembled gun into my house, I by no means think that you were out of line not to.
Mama, homeschooler, midwife. DD (13yo), DS (11yo), DD (8yo), DD (3yo), somebody new coming in November 2013.