The author is using "castration" figuratively. Gun owning men are generally psychologically healthy; they are not making up for a sexual inadequacy, as women and sheep in general like to claim; rather they are following the masculine impulse to defend themselves and their families and their own. Men who perceive that they are called to be warriors will of course seek adequate means to enable them to be such. The author of this piece as well is not subscribing to the view that a gun is a surrogate for sexual potency. Can we say that instead the imagery is a projection by those who oppose gun ownership? Misandrists, especially, like to belittle men by attributing a small size to their penises and so on. Those who vehemently fear the power of men cannot but reduce masculinity to the male sexual organ .
I've heard this version on the radio (KOIT), but also an updated version as well, in which some of the lyrics are updated ("Jazz in the Fillmore"). As soon as I heard it for the first time (which was this month), I was annoyed. My reaction hasn't really mellowed since then. It's a sappy 'holiday' song trading on nostalgia, and sounds exactly like cheap lounge music - a Christmas song, like many others, which is focused on us and glorifying our mundane experiences, instead of Christ. Some may think of it is a "golden oldie," but it's another isntance of our cultural and civilization decline.