The two answers are as follows
"he was afraid that diem's defeat would cause communism to spread to other parts of asia"
and also
he did not want chi minh, a communist, to gain control of south vietnam
Http://americanhistoryrules.com/unit5/docs/PopulistParty.pdf this really helped a lot...
Registering to vote in one’s home state
I believe you meant the red scare"" ... it was mass hysteria scare over the spread of communism in the US and the rest of the world