why did censors object to cyanide reference?

My guess is that the censors did not want to "educate" the public about the potential uses of this commonly available compound. Potassium cyanide and sodium cyanide were widely available for use in electroplating and photography. Much of the world's gold is extracted from ore by means of a chemical reaction with cyanide salts dissolved in water ("heap leaching"). When cyanide salts are mixed with acid, the poisonous gas-hydrogen cyanide (HCN)-is generated. Calcium cyanide [Ca(CN)2] is unusual in that it generates HCN when exposed to water. This compound (tradenamed "Zyklon B") is what was used in the Holocaust death camps. In my career as a lab technician, I have worked with cyanide in chemical synthesis; hence my interest in the subject.