The 2nd Amendment was passed at a time when it was still possible for the civilian population to stage an uprising and topple the government. It is now no longer possible. The 2nd Amendment is now, therefore, outdated and its only use seems to be a (rather dubious) justification to resist gun/arms control.
For a laugh, you might wanna take a look at this video.
YouTube - Archie Bunker vs. Gun Control