Really?
Are you sure its not just a case of guns being ingrained in American culture and make the owners feel all macho and strong, and that any old excuse is good enough to argue that they should be allowed to keep huge pointless arsenals of weaponry?
I mean, from what I can tell, such people are generally on the right of politics, and at the same time they argue that they need guns to protect against a threat from within, they believe Obama is a non American, communist, Muslim. Well, er, wouldn't that be a great threat from with in to the US? Where were these citizen protectors of American freedom when Obama the commie Muslim took office? Shouldn't they have been using their arsenals to protect America? Or do such people actually know they are taking nonsense?
On top of that, when in the last, say, 100 years has the US government posed a threat to American citizens, such that they citizens needed to break out the weapon to protect them selves?
Frankly I think its more to do with male machismo, culture and being stuck in the 17th century. They have always had guns, and what ever logic you argue with, they simply don't want to change. If you managed to convince then that the government isn't out to get them, they'd just find another excuse.
It reminds me of fox hunting in the UK, or bull fighting in Spain. All these things defy reason, logic and decency, but we all want to hang on to them, simply because they have always been there. Heh, its kinda like saying you can have music any more.
I'm sorry, people may claim they want guns for the reason you cite, but I honestly don't believe them at all.