BK: What design aspects of the AR-15 make it menacing? The low recoil? The modularity? It is one of the least powerful centerfire rifles you can buy. Killing effectiveness at 100 yards is <20% of that of a 30-06 round (formerly used in battle rifles, now just used for hunting)
Here are the facts
1) The 2A has nothing to do with sport or hunting. It has to do with the ability of the citizens to form militias equipped to engage in infantry combat. This means we were intended to have infantry weapons comparable to what the military uses. Many of the revolutionaries used "kentucky rifles", which were dramatically SUPERIOR to the "brown bess" muskets the Brits were using
2) Rifles, of which assault rifles are a small subset, account for about 3% of gun homicide. Even if you could wave your wand and make all rifles VANISH, AND make criminals so stupid that they didn't realize they could use another type of weapon to kill someone, gun homicide would be reduced a whole 3%
3) It's dangerous to set a precedent of having the government break its own laws, especially laws intended to limit government power and protect our freedom, starting with the Bill of Rights no less!