The true purpose of the Second Amendment to the U.S. Constitution is to preserve the concept of the citizen militia, an armed citizenry willing and able to defend its rights against enemies foreign and domestic.
Citizen militia have a long history.
Rather than being obsoleted by modern technology and industrial civilization, militia can now easily include anyone who wishes to help, including women and the elderly. With the recent rise of gun control legislation, a grass-roots movement has arisen to reclaim the tradition of the citizen militia. The media stereotype of a militia, however, only serves to keep people from understanding why it's a good idea to have as many checks as possible on the power of government. It's just not my style. So don't ask me how to get in touch with one, because I have no clue.