I recommend Judge Napolitano's entire article, but here's a taste:
The historical reality of the Second Amendment’s protection of the right to keep and bear arms is not that it protects the right to shoot deer. It protects the right to shoot tyrants, and it protects the right to shoot at them effectively, with the same instruments they would use upon us. If the Jews in the Warsaw ghetto had had the firepower and ammunition that the Nazis had, some of Poland might have stayed free and more persons would have survived the Holocaust.
Most people in government reject natural rights and personal sovereignty. Most people in government believe that the exercise of everyone’s rights is subject to the will of those in the government. Most people in government believe that they can write any law and regulate any behavior, not subject to the natural law, not subject to the sovereignty of individuals, not cognizant of history’s tyrants, but subject only to what they can get away with.