Russia openly opposes a European missile defense system. It's the old Cold War tactics all over again. The missile defense system that was installed in the 80s inflamed tensions with the Soviet Union, and now this new missile defense system will inflame Russia, and we're in even more tense global situation than we were in the Cold War!
A missile defense system near Russia is actually less effective. Once missiles are launched, they are too low and could be incapable of being intercepted. At higher altitudes, say over the Atlantic Ocean, any ICBM launches will be sitting ducks for any missile intercepts. Russia opposes any European missile defense system for fear of any missiles that could target sovereign Russian territory. Their fears are misplaced.