The pro-gun community opposes this because the intent of 2A was always to protect the ownership of militarily-useful arms.
The gov't already has the right to raise and provide arms for an army, as part of article 1 of the constitution; claiming that 2A protects the gov't's right to arm itself, when it was already granted that right earlier in the constitution, is laughable. Militias were groups of armed citizens, separate from the army, and they were often expected--and legally obligated in some cases--to provide their own arms in serviceable condition, and to train themselves in their use.
The way to effectively curtail violence without curtailing rights is to change the circumstances that lead to violence. Yes, you can cut out lung cancer, and even possibly do a lung transplant, but it's far, far easier to prevent lung cancer by not smoking than it is to cure it after you've been smoking for 50 years. Same with violence; look at the factors that lead people to pick up and use a gun illegally, then work to prevent those, and you'll have a greater net effect.