You have acquired an in-depth knowledge of the Salem Witch Trials as well as the House Un-American Activities Committee trials and McCarthy investigations. You've learned how mass hysteria can cause intolerance, governmental abuse of civil rights, and extremism can corrupt the concept of justice. It can turn families against families, friends against friends and twist a noble cause into something ignoble.
Mass hysteria, thankfully, does not occur very much. However, it is a dangerous thing for it to occur and if it should occur again, the public should know how to calmly deal with it. You, at least, are now aware of the phenomenon and know its features. It is up to you to educate your friends and family on the issue and spread the knowledge you have gained. Don't get swept up in media sensations or listen to those who are uninformed on the issue. Use your critical thinking skills and learn about the problem yourself. Then logically and rationallydeal with the situation in a calm manner.
In order to learn more about human behavior in panic/mass hysteria situations, I recommend the following books and Wikibooks article:
Anthony R. Mawson, Mass Panic and Social Attachment, Ashgate Publishing, 2007
James B. Rule, Theories of Civil Violence, Berkeley, University of California, 1988.
Clark McPhail, The Myth of the Madding Crowd, New York, Aldine de Gruyter, 1991