As a veteran of the US Army, I would never turn my rifle on my own people unless they had already been shooting at me to begin with for some criminal reason. No order given in that respect would ever get followed by me or my soldiers that I commanded. Those that never served may not understand, but most soldiers would never do anything to harm their own. That doesn't mean no soldier, marine, airman, or sailor would follow that concept but most and by most, I mean almost all of them would not hurt or round up their own citizens without some major due cause.
