What about invasion? You can't trust the government to do the right thing? And well, if there's a bomber heading straight for your village, you'll be fucked if you're waiting for the armed forces to come save you. Heat seeking missiles will come in handy. These things have happened before, no doubt they'll happen again. Pearl Harbour was practically defenseless against the Japanese, people in the UK had to retreat from the main cities or into bunkers during WW2 because of the Germans bombing them - think how different things would be if people could defend themselves in those situations?
The second amendment was put in place for similar reasons, the US feared invasion from the British, you couldn't rely on the military to protect everyone or cover every entry from where the British might send their forces, hence it became a right to possess your own firearm. Today's threats are very different, I mean, newly independent America didn't have aircrafts to worry about or people bombing their towns and villages, I don't think a gun would take down a Russian bomber, or any thing the middle east, China or Korea may wish to throw at us. Having missiles is well within your right to bear arms, surely?