Truman Doctrine: Fear Quotes

How we cite our quotes: (Sentence)

Quote #4

Collapse of free institutions and loss of independence would be disastrous not only for them but for the world. (85)

Why is this quote in particular so frightening? What does he mean the collapse of free institutions would be disastrous for the world?

Quote #5

We must take immediate and resolute action. (88)

Or else what? Why does Truman sound so grim? What is going on here?