Estonia is a parcel of land which can potentially control the passage in the Gulf of Finland in the same way as Iran’s controls the world’s most important oil artery — the Strait of Hormuz. Until today two factors restricted this control — 12 nautical mile territorial limit and lack of armed forces of any significant strength on Estonian territory.
In case of Russia’s excessive response, both limitations could easily be removed, the Gulf of Finland will then be divided between Estonia and Finland, and in case if Russia attempts to forcefully resist the measure, as a member of the NATO alliance Estonia would get a justification to invoke the NATO charter and ask for help, and there can be no doubt that the help would be forthcoming immediately.
This could lead to two possible scenarios: either a full scale world war or Russia’s return to the times of the Peace of Stolbovo of 1617 under which terms Russia lost all access to the Baltic sea.
A selective democracy is hardly a democracy at all and a «state» where one third of population is disenfranchised on a whimsical technicality can hardly be considered either democratic or free. As I know both societies intimately well I can say with a degree of confidence that most Russians (or modern Americans, Austrians, French or Germans) cannot comprehend what it is like to be of wrong ethnicity and live under state tyranny in an ethnocracy. A friend of mine was born in Estonia from parents who were also born in Estonian SSR in the 1950s. 
