But we leave after trying to install a democratic government, it worked in S. Korea and Japan atleast...This proactive "defensive" move was essentially the basis for the US invasions in Korea, Iraq, Afghanistan, and Vietnam and nearly every other skirmish the US has engaged in for 50 years. FYI.
Also, do you think anyone in S. Korea thinks Communist China should control S. Korea just because they are close by? Or many people in Latvia think leaving NATO and becoming a close ally of Russia is a good idea, just because they share a border and it would make Putin feel better?
No democratic nation wants to be under the thumb of a neighboring country led by a dictatorship, or communist party.... So I think its a good principal to help them in their defense of their own freedom.