The arming of white America began in earnest after the rise of the black
> movement for civil rights.
>
You're partially right, but not for the reasons you imagine. I don't think anyone has satisfactorily explained why, but predominantly white gun owners, organized by a politically-reoriented NRA, reacted most strongly to a racist backlash against black gun ownership in general, and the armed wing of the Black Power movement in particular.
Before 1977, the organization was a gun-control lobby. Believe it or not.
http://www.theatlantic.com/magazine/archive/2011/09/the-secret-history-of-guns/308608
-- "Hige sceal þe heardra, heorte þe cenre, mod sceal þe mare, þe ure mægen lytlað."