I'm sure that you have heard the quote "What, sir, is the use of a militia? It is to prevent the establishment of a standing army, the bane of liberty." Rep. Elbridge Gerry of Massachusetts, I Annals of Congress at 750 (August 17, 1789)
There is a reason for that belief.
And what exactly is that reason?
Do you believe that an informal militia, the private ownership of arms, is an effective way to keep freedom? Even without the willingness to use them? In a world where your bolt-action .243 is up against helicopters, nerve agents, tanks, and morter fire? In a world where the media will demonize the resistance fighter, and teach the American people that this group is composed of terrorists who hate America, irregardless of whether constitution is on their side?
Maybe when that quote was written, it applied. When we all had access to the same pointy sticks, and there was a relative balance of power between the armed civilian population and the force of the government. But today, that power isn't balanced. We still have pointy sticks, but the government has much more effective tools.
Governments gain and remain in power by monopolizing violence. They want to be the only group who can apply violent force in their sovereign land. If anyone else lays claim to the threat of violent force, they must be marginalized and eliminated, less they challenge the absolute authority of the government. That absolute authority can't exist when the citizens retain an effective means to violent force. The problem is, effective is a relative term. What was effective in 1789 isn't effective today, because power is not balanced. Our side (citizenry), has remained stagnant due to laws, but their side (gov't) has by far technologically overgrown that barrier.