The fox in the henhouse must pause to calculate: kill them all and eat at leisure, or eat as many as possible before the caretaker comes. If there are less than seven, there is barely a hesitation; they are all dead before a significant cry can be raised. If there are twelve, it may be more profitable to eat three or four while the others squawk — otherwise the seemingly prudent killings would be cut short by the arrival of those who would object.
In a henhouse of thousands the calculus is altogether different. The shrieks and squalls of the living are ignored by their caretakers. A fox may feast as it pleases. The farmer assumes that some chickens will be lost, and this is accounted for and accepted.