Why were critics expressing discontent with society in the 1950s

The 1950s was a time of widespread fear and anxiety - the two great powers, the USA and the USSR, were held together in M.A.D. (Mutually Assured Distruction), thanks to the US dropping the two nuclear bombs on Japan, fascinating Soviet scientists into developing their own Nuclear weapons program. 
Joseph McCarthy, a US Senator from Wisconsin from 1947 until his death in 1957, played a huge role in establishing a sense of uneasiness and paranoia among Americans in the 1950s, at the possibility of spies lurking within society. Individuals became more individualistic, and trusted authorities less and less - domestic crimes, for example, were often solves by individuals rather than these individuals requesting help from the police. Actors, those in the entertainment industry as a whole, and politicians were by far the most targeted by McCarthy's policies of kidnapping, torturing and extracting information, if there was a suspicion that those being kidnapped were in fact Soviet spies. The overwhelming majority were not, but there were still a handful that were. The government of the USA attempted to hide the innocent victims of these kidnappings, but were not very successful, and as such, individuals became extremely weary of authorities.

To sum up:
- Cold War begins, USA and USSR battle each other with espionage and intelligence rather than all-out warfare
- American government becomes increasing suspicious of spies within Entertainment industry and internal politics
- These paranoia-inducing policies were widely unsuccessful, and as such, fermented distrust for authorities within American society, and among societies of American allies, who were also suspicious of spying.

If you need further information, a quick search of McCarthyism or the 1950s social context of America should help.

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