I agree with what you have said(except the last part).

Ask yourself, what does a government require to kill its own citizens? It can't do it by default. It needs the POWER to kill its own citizens.

In a government like the USA in 1776, where the states have much of the power(and any powers not specifically given to the Federal Government, are delgated to the States), the Federal Government CANNOT kill its own citizens.

In a government like the USA in 2016, where the Central Government has been given much more power, it has the power to kill its own citizens.

Simply put, a weak central government(like the Confederacy the preceded the United States, or the United States, as they were created in 1776), cannot have the power, or right to kill its own citizens. Only a Strong, CENTRALIZED government (like the Nazis, or Soviets) have the POWER to kill their own citizens.

If the Nazis were divided into states, that had more power than the central governments, the individual states could have stopped Hitler from killing Jews. But, the Nazis were not divided as such, and it was one big Centralized Government, with not checks or balances, so nothing could be done to stop him.

Hope this helps, as you don't seem to be understanding what I say.