My family enjoyed watching the movie Argo. I liked the beginning which gave a very brief historical background to the taking of hostages in the American embassy in Tehran. After Iran democratically elected a Prime Minister he nationalised oil industries owned by British and American companies. This led to CIA staff based in the embassy engineering a coup in 1953 and re-establishment of the oil companies and the rule of the Shah who used his secret police SAVAK to brutally crush dissent, including with torture.
The movie shows many scenes [some from actual historical footage] of angry and "fanatical" Iranians demanding justice, burning Uncle Sam effigies, storming the embassy, .... Some have criticised the movie as portraying stereotypes.
Learning just a little of the historical background helped me understand why they
were so angry.