i'm not defending the constitution for the sake of defending the constitution. i'm not really "defending" anything. i missed the "magic wand" posts above.
i'm just speaking practically. if people want to go out and repeal the second amendment, go for it.
that said, comparing the US situation to australia is bold. australia is estimated to have recovered something like a quarter of its citizens' guns, which totaled roughly a million of them. the US has 350 million guns. so even in this alternate reality where (1) the second amendment is repealed, (2) congress enacts a ban, and (3) our efforts are as successful as Australia's, the number of privately owned guns in this country will still number in the hundreds of millions.
i'm not a huge pro-gun guy. i don't have a gun, i've never been hunting...the constitutional right means nothing to me. but given the prevalence of guns in this country and the long-established gun culture that's firmly entrenched here, i think it's next to impossible to put the "gun problem toothpaste" back in the bottle.