Panetta went to Afghanistan and made the combat troops disarm before they could be admitted to his august presence. Combat troops are armed because they are in combat – or at least in a combat zone.
If you do not trust your own military, who can you trust? A personal bodyguard of private mercenaries? If you cannot trust American citizens to protect and defend the constitution by force of private arms, who CAN you trust? The TSA?
This was covered in 'The Prince' by Machiavelli. It was also covered, more historically, in 'The Art of War' by Sun Tzu.
When you can no longer move freely in your own country as a politician, you are doing something wrong. Attempting to subdue the citizens at that point is a failed strategy. We already know that someone is going to die. Eventually it will be you.
In a democratic Republic, the citizens own the government and decides it's direction. Anything else is autocracy. The Republicans have failed as a political party by pandering to fringe radicals. They are done. We can either work together and begin the healing process or go directly to the next civil war – in which no one will win. I suspect that it's already on.