How justified was the fear of Communism during the Cold War?

by hahaha01357

In terms of both its ability to foster revolutions domestically and spread revolutions abroad?

Edit: Removed follow-up speculative question.

Searocksandtrees

And would these regimes have been as violent and repressive had they been allowed to peacefully attain power through open elections?

Hi OP, can you strike out this follow-up question? This subreddit does not permit answers which are premised upon speculation; you might consider taking that part of your question over to /r/HistoryWhatIf. Thanks!