I actually just read an extremely interesting article at Slate that puts the entire statement in historical context within the insurrectionist theory of the 2nd amendment held by the Republican party, something that the founders and Supreme Court disagree with. It truly emphasizes the seriousness of the comment in ways I hadn’t realized without even bothering with the “horrible day” sentence.
Taken at face value, all of this rhetoric adds up to one very clear belief: If you believe the United States government has grown tyrannical, the Second Amendment protects your right to rebel violently against it, using firearms, to reclaim your liberty. Cruz and his ilk rarely specify precisely what this revolt would look like, but the implication is extraordinarily clear: Armed Americans should shoot enough government officials as is necessary to overthrow perceived oppression. The Cruz-endorsed insurrectionist theory of the Second Amendment, in other words, is basically a tacit permission slip to assassinate political leaders whom one deems to be oppressive.
And that, it seems, is precisely what Trump implied on Tuesday. Should Clinton get elected and appoint ostensibly oppressive Supreme Court justices, the logical conclusion of the insurrectionist theory is that “Second Amendment people” should use their constitutional right to resist tyranny by shooting the president or her judges. One man’s president is another man’s tyrant, and the GOP’s current framing of gun rights quite explicitly licenses an armed revolt against tyrants. Oppression, much like the Second Amendment, is in the eye of the beholder. And Trump has just given his very eager supporters another excuse to view Clinton as a tyrannical oppressor—and given instructions to act accordingly.