When it comes down to it, Barack Obama and conservatives operate from fundamentally different cognitive triads: they don't agree about what America ought to be doing, they don't agree about what its role in the world should be, and they have different preconceptions about what will happen in the future.
On Russia, conservatives -- broadly here -- believe that our relationship is fundamentally adversarial, and will remain adversarial, because it's in the interests of Russia to be adversarial. In this view, Russia is dangerous, is doing dangerous things in the world, is allied with dangerous people, and views the world through a bipolar lens. The sensibility of an adversary must never be placated unless it measurably increases your security. To concede unilaterally always appeases the adversary because it fortifies their will. America can never appear weak; it can never appear humble; it must lead by example; it must honor its commitments to its allies; it must always project strength, lest it become just like every other country -- that is, unexceptional -- and therefore unable to serve its destined role in the world. What separates the Russia of today from the expansionist, imperialist Russia of the Cold War is a fear of U.S. power. Also: they believe that missile defense systems really work -- or, if they don't quite work yet, will work -- and don't understand why, given the chance to design a system that will protect the country from ballistic missiles, anyone could possibly oppose it. Assuming that adversaries will act rationally is naive, and conceding them to is tantamount to surrender.
For Obama, strength is projected through the exercise of a larger set of values. He does not believe that a humble country -- and here he shares a view with George W. Bush pre-Iraq -- is necessarily a weak country; he does not believe in projecting military strength for the sake of projecting military strength. He does not believe that the cultivation or fear, or brinkmanship, ought to be the basis for policy. And though he doesn't quite admit this, I don't think Obama subscribes to a providential view of America's role in the world -- one that exists prior to policy, or prior to history. So Russia's interests can be reconciled with America's interests. And if, in the furthering of America's interests, decisions are seen as concessions under the old metaphor, so be it. American interests are no less concrete: in this case, Obama believes than Iran is a much larger threat than Russia; it believes that money ought to be spent to deter Iran's likely capabilities; it believes that overmatching deterrence technology would encourage Iran to get up to speed more quickly; it assumes that, by locating a radar station and missile battery up north, tensions with Russia will increase; and that, if anything, removing the missiles gives the Russians one less way to avoid the pressure for them to act against Iran. From the standpoint of security, the U.S. and NATO actually have a freer hand to respond to any provocation by Russia.