The justification for this project is, unsurprisingly, to protect Eastern Europe from rogue states such as Iran or North Korea. A rather odd claim, considering the positions of those two countries. North Korea has recently had successful missile tests, but their capabilities are certainally nowhere near what is needed to attack Eastern Europe. Iran is in the same situation, but even further behind in terms of technology.
Now, does anyone honestly believe, propaganda against these two nations aside, that other government would be stupid enough to launch an attack that would result in their near instant annihilation? North Korea's nuclear program exists solely as a bargaining chip to secure desperately needed aid, and Iran's exists as a deterrent against western pressure on its policies.
Of course, the average western government, along with most media outlets, paint the leaderships of these two countries as bloodthirsty extremists, capable of doing anything. At the moment, Iran doesn't even have nuclear capability. If, for some reason, Kim Jong-Il was to take immediate leave of his senses and dream up such an attack, and, ignoring the obvious technological issues, the vast majority of North Korea's generals would commit a military coup faster than you can blink, considering the alternative of having their nation turned into the world's largest nuclear wasteland.
So, what is this proposed system for? Well, over the past few months, the American government has becoming increasingly critical of what it views to moves towards authoritarianism in Russia, and this is clearly a sign of discouragement. Putin's reaction is unsurprising.
Of course, NATO and the US will ultimately play dumb, but Putin, having experienced the Cold War first hand, is hardly a foolish man. Honourable or not, the outlandish claims of the proposed defense system are a rather flimsy cover for a message to Russia. Putin's threat may not be very noble, but it is hardly surprising. To appear weak to a world that is increasingly isolating the Russian state, one that could have easily become an important ally in the post 9/11 world, is not something an ex-KGB official turned President is likely to do.
I could go on for quite awhile, but instead I'll leave you with the very insightful thoughts of one Mikhail Gorbachev, and invite you to add your own.

