The Second Amendment after the San Bernardino Shooting

The recent terrorist attack in San Bernardino, California, sparked a new wave of controversy over the Second Amendment and the gun control debate in the US. Democrats, who are associated with the center-left of the liberal American establishment, have made perfect use of this tragedy in order to promote the idea of limiting or even banning firearm ownership.

Gun ownership rights, not 'Islamic' Terrorism, to be blamed

Whenever these sorts of incidents occur in the US, and these are increasingly common, the main discourse in the pro-establishment media always rehashes the same talking points: such a tragedy would not have happened if the criminal wasn't able to buy a gun. Obviously, this is a classic substitution of concepts: the establishment media will not blame the source of crime (radical Salafist groups and government policies towards them), but instead makes a secondary issue (relatively easy access to guns) the main point.

Destroying the last remnants of the constitution
One of the main objectives of modernist, liberal discourse in general is eliminating all kind of identities and traditions.  In this case, liberalism has begun to devour itself, moving from early modernity into modernity proper, and then into post-modernity.  The post modern phase may include self-cannibalization or auto-alienation. America is an interesting case, like some other New World states - it was created from the start already in modernity.  In American society, the Second Amendment and gun ownership in general is a cornerstone, the importance of which is difficult to overestimate.  America, born into modernity, understands on day one, that the government and the people are in their most natural state when they are at odds with one another. 
America may not exactly have homogeneous traditions in any meaningful sense of the term, but there are some social threads, created during early modernity, which are under assault now in the present period. The establishment powers now try to use any opportunity to attack and eventually destroy these threads, which exist today partly in the US Constitution, and which have been integral in American society for centuries. The Second Amendment is only one of several which many constitutional experts have warned have been under attack by successive court rulings, for many decades.  As an aside, within the anti-gun hysteria milieu are some feminist groups and scholars, who even say that a firearm itself is a phallic object, that its wielder is compensating, and that it should be abolished as an offensive (sexual) object.
Security against tyranny
The Second Amendment of U.S. Constitution says: "A well regulated militia, being necessary to the security of a free state, the right of the people to keep and bear arms, shall not be infringed". 
It is important to understand that the US Constitution is a document which elaborates the limitations on government, and powers which are not specifically named, do not exist unless they are directly implied.  The term 'infringement' is also important in legal language, because an infringement is any shortening or curtailment, not simply an abolition as would be the extreme case.  However, successive Supreme Court rulings in the US have effectively already curtailed, i.e., infringed, upon this right, and others.
Thomas Jefferson also held that because governments may, as a rule, degenerate into tyranny, people would be in their moral-legal rights to rise up in an armed revolt against tyrannical authorities. He believed this was cyclical and may even be necessary several times within a person's lifetime. It is important to contextualize this in English history, which saw the Civil War, the Monmouth Rebellion, and the Glorious Revolution all in a span of forty years during the second half of the 17th century. 
In many ways this makes the Second Amendment perhaps the most important of them all.  The Second Amendment effectively strips the state of a monopoly on the use of force, and citizens theoretically rely on the Second Amendment as a guarantor against tyranny.  In the event that all other Amendments had been effectively infringed or abolished, still having the Second Amendment, the people could still effectively threaten the state physically, or even force a change of power towards a constitutional government. U.S. citizens have more that 300 million firearms which means that on average, there is a gun for each American. The U.S. government has increasingly worked against the constitution, framed by the first generation of Americans after the revolution.  The government understands that it will find it generally difficult to oppress or put down any armed and trained citizens, so in this manner the establishment solves the problem: by banning gun ownership. History has numerous precedents when after banning guns and collecting them from the population, the government turns into an openly oppressive tyranny with a monopoly on violence. It is not surprising then that a government that has turned away from a constitutional government would attempt to undermine the only effective physical mechanism which the people have as a guaranty against tyranny.