If we have any duty at all it to fight against all sort of injustice. Funding the mafia and orchestrating terrorist attacks to scare off people in order to stop "communism" to me sound just as scummy as your idea of communism you claim we have a duty to stop.
Anyway I encourage you to learn history and learn about communism, read Marx books. You are not supposed to like it or agree with it, just read it to actually understand what it is about
The nazis were literally stopped by stalin and his troups. Could you explain how communism is so bad that orchestrating a terrorist attack against civilians and murder childrens to blame them is justified?
Nato and usa tried to stop "communism" with the help of former nazis.