Come up with a Scenario to Show Private Guns are a Defense

  It is said and repeated: Before taking over a nation, the government takes away guns from the people.
  And, there you have it: We cannot ban guns here in America, for that would precipitate the downfall of our nation. End of discussion.
   Is it true? If we banned guns in America, what would happen? To begin with, the federal government is already in charge. So, to suppose that they are going to take charge -- well, they already are in charge.
   What you must mean, then, is that the federal government will take our freedoms once it has our guns. Or, do you mean it will be easier to haul us off to jail? Just what do you envision happening? If we are to lose our freedom of speech, or freedom of religion, or freedom of movement, what events are to happen, and how is the gun going to stop them? Suppose we banned guns, and no one had a gun. Suppose the government then said, "You have no right to oppose this government and we are going to haul you off to jail."
   I think of the journalists who have lost press credentials during the Trump administration. They expressed themselves against Trump, and lost their credentials as a result. Would it have done any good if one of them had pulled out a gun, and said, "You can't do this. I have a gun"?
   If you fear we will lose our freedoms if we lose our gun, I wait. Come up with a scenario where freedom of speech or freedom of religion is being lost, and someone steps in with a gun and saves that freedom. Or, maybe it is a mass of guns and a private militia stepping forward to save a nation. But, I want an example of what might happen.
   Red Dawn? I believe the story line there has it that America's military is struggling, and the citizens step into help fight for their country. I don't see how that story proves freedom will be lost if guns are banned. It does suggest, though, having guns allows private citizens to step in and help if America's war machine is ever challenged. I wonder if even that story line is a strain. Could a populace armed with hunting rifles, or even AR-15s, stand up to Russia's military might if the U.S. Army was not holding off the foe? 
   Come up with a scenario. Tell me how our freedoms might be lost if we don't have guns. I'm not saying you can't, I'm just saying I'm having a difficult time realizing what that scenario might be.