NATO missile defences are present in the eastern block (Poland, Czech Republic, etc) and AFAIK those can be repurposed to launch offensive missiles as well. If having offensive missiles in a country takes 2 steps, where the first is gaining military access to said country and the second is to install offensive missiles, certainly the first step is the harder to accomplish.
Additionally, when it comes to geopolitical power things are much more complex than you make them to be. I suggest reading this publication[0] to understand better what's going on.
A few points:
> Moscow claims that missile defenses represent an American perception of threats from Russian nuclear missiles. Therefore these defenses aim to neutralize them in potential conflict. Either Russian missiles would be attacked by a conventional air and space first strike, possibly involving these networks in Europe, or else these missile defenses would frustrate a retaliatory second strike leaving Russia defenseless.
> While these missile defenses in and of themselves are no threat, they represent the first stage of a planned or potential U.S. buildup of a missile network in Europe that could then neutralize Russia's first and/or second strike capabilities as cited above and shift the burden of war to Europe.
> If missile defenses were stationed at these bases, it would create a pretext for stationing offensive missiles there. This would force Moscow to assume the worst case scenario and could cause Russia to attempt to shoot them down leading to a conflict with America.
> These defenses and whatever may follow them rupture the fabric of strategic stability where neither side has the freedom of action or margin of superiority that might encourage it to think it could employ coercive diplomacy or military force with impunity. That strategic stability equation is of critical importance to Russia because otherwise Washington might be tempted to think it could strike at Russia with relative impunity.
> Finally, there is a fifth, and always unstated but critical aspect here. These defenses entrench the United States in Europe's military defense and foreclose any prospect of Moscow's being able to intimidate or reestablish its hegemony over Eastern and Central Europe, and even possibly the CIS. If missile defenses exist in Europe, Russian missile threats are greatly diminished if not negated. Because empire and the creation of a fearsome domestic enemy are the justifications for and inextricable corollary of internal autocracy, the end of empire allegedly entails Russia's irrevocable decline as a great power and, (the crucial point) generates tremendous pressure for domestic reform.
.0: https://www.wilsoncenter.org/publication/352-missile-defense...