"...The practical reason for the Second Amendment is that private ownership of guns was necessary to perpetuate slavery."
I cannot let this go unchallenged.
The practical reason was that the Founders had just won a war against the most powerful nation on Earth starting with a privately-armed militia. They knew from strong, recent experience that a people well practiced with arms they owned were the first defense against tyranny.
Concorde -- "the shot heard round the world" -- was fought over a gun-control action: the British trying to confiscate privately owned arms and put them into an armory they controlled.
I agree with your comment to this extent: citizens should be able to possess the current military issue-weapon. In our times, that would be M-16s, or at least its semi-auto equivalent, the AR-15 and clones thereof.
(Hey, Mr. Obama! Want your new mandatory-volunteer corps to be actually-volunteer? Set it up as an Article 1, Section 8 militia, and let volunteers keep their issue weapon after their training hitch in high school.)
In any event, times have changed. The very first gun control measures were laws keeping guns out of the hands of slaves, indentured servants, and Indians. Many modern gun control laws were originally enacted after the Civil War to keep guns out of the hands of freed black men.
One of the reasons given in the infamous Dredd Scott decision for not accepting black people as real human beings was specifically that then they'd be allowed to possess arms under the Second Amendment.
In my own lifetime...look up Deacons For Defense and Justice, armed black churchmen who rode with other, more pacifistic civil rights activists as body guards.
In the current case, scroll down through this thread and read the comments from those who would use their arms on the school thugs who perpetrated this vile sex crime. That's what the right to keep and bear is about -- not revolution, not overthrowing the government, but checking it, returning it to its limits. Reminding officials who might otherwise think themselves above the law that there are consequences beyond the law. Yes, the citizens imposing those consequences would be in prison or dead themselves -- but that's exactly what Jefferson was talking about when he said the Tree of Liberty must occasionally be watered with the blood of tyrants and patriots.
(And, yes, I agree one hundred percent that sex-offender registries are also abominations, but if we're going to have them, the two women who actually performed the search and any school official who approved it should damn well be on one, if they survive prison.)