No other historical event is illegal to critically examine. The accepted view protected by law is that a policy of mass killing of prisoners resulted in a holocaust. An opposing view asserts that no such policy existed and deaths were a result of a typhus outbreak and the holocaust was invented to distract from real atrocities.
Having ones health and livelihood sustained by government programs is a major factor in the left/right divide. Hostility and ridicule towards a liberty minded and self sufficient skeptic is a way of maintaining the dependence. Whereas a person able to critically analyze and question anything unafraid of truth is a threat to every single dependent person.
S.S.R.I.'s are prescribed to about 10% of Americans in order to suppress or elevate moods and emotions. Most notably for treating clinical depression. What other emotional responses are possible in some people? Suicide is listed as a possible side effect but not homicide.https://www.naturalnews.com/039752_mass_shootings_psychiatric_drugs_antidepressants.html