<span>"decapitation of the government" is the idiom Jay Winik used in the second paragraph. The idiom's intended meaning is the severance of the top government officials from the remainder of civil society through assassination. I think the idiom was chosen to add a grave visual description of the sense of the moment.</span>
Ruth explains to Mr. Thorpe that he is now in homesteading country and people in there take care of themselves, so they are not willing to accept his help or change their ways. She stays firm to her convictions and explains this to him in a respectful way.