I think you're hyperbolizing and demonizing for no real good reason here, varwoche.
Given the reports of violence, arson, and riots on TV - especially in this age of partisanly targeted news reporting - I'm not at all surprised that people might feel threatened by a crowd of protesters on their property. If a crowd of protesters had come across my property... I likely wouldn't have been outside, but I very likely would have been armed, just in case.
The most frustrating thing is that there's so much spin involved in every story, that you end up with news that's tailored to increase outrage. Media targeted to liberals will portray those two as psycho, racist, gun-nuts who are a threat to everyone and clearly unhinged. Media targeted at conservatives will portray them as upright citizens defending their home and their lives against an unruly mob of violent rioters.
Reality is most likely an older couple who are afraid that a protest could turn ugly (thanks media!), and want to prevent that from happening by making sure that the protesters are aware that they're armed. Not great, but not as bad as it got painted either.