A lot of people have no problem rounding up a mob, maybe beating them up, and tossing them in jail; a lot of those same people will think twice before saying "We can't go in on the ground... I want to be a part of clearing that mob by bombing it to pulp".
Or else an exodus of the leadership and rank-and-file soldiery on par with the Southerners that resigned in '61.
I wouldn't hold my breath expecting, say, MSNBC to give extensive sympathetic coverage to domestic "insurgents" who don't share their political views. The vast majority of the Tea Party did nothing more than yell at congressmen and hold rallies where they got all the official permits and cleaned up after themselves, and yet they were uniformly regarded in the news media as the second coming of Timothy McVeigh. Imagine how the media would treat them if they did anything more with their guns than the occasional dumb open carry stunt in Texas.
It's just the incidences of slaughter they - perhaps optimistically given the US status quo - believe may be reduced through gun controls are actually happening on a not infrequent basis, whereas the Second Civil War scenarios are wildly unlikely fantasy.
People believe social media campaigns might work precisely because they don't think that the only thing keeping the US from turning into a fascist police state is consumer weaponry.
That's a reasonable opinion, but one I disagree with. A second secession movement and full-blown Civil War will probably never happen, but martial law ordered in response to protest or active resistance of a law is not unthinkable. The risk of death by gun violence in the United States is dwarfed by the risk of death by automobile accident, heart disease, and so on. I would absolutely rather live in a country of ~320 million with a few thousand deaths per year due to gun violence, than in one with no weapons to deter martial law. I'll take a small (blown out of proportion by the media) threat over an existential threat any day.
And that's even assuming that you could make gun violence disappear entirely overnight. Revoking access to registered firearms could very well reduce the number of spree shootings, but would do little to affect the black market supply used by criminals in robberies and turf wars, and probably increase the amount of gun violence used in robberies (as criminals would then be sure that no one would be able to resist them).
As such there is no cognitive dissonance as propping up a country is different from crushing all opposition.
Mind you, last time I ran the numbers, it was safer to be in Belfast during the troubles than in Detroit over the same period.