Possible Clues:

• McCarthy era paranoia
• It led to the blacklisting of Trumbo and Chaplin
• '40s-'50s paranoia
• Post-WWII fear of infiltration apparently confirmed by four puzzle answers
• Post-world-war paranoia
• *Fearful 1917-20 period
• 1950s paranoia
• Old anti-Communist reaction
• Paranoid period
• Old fear of Communism