Honestly asking: What is the specific harm involved here that is deserving to be taxed? How would we measure this harm in order to know how much to tax a give

Honestly asking: What is the specific harm involved here that is deserving to be taxed? How would we measure this harm in order to know how much to tax a given company? Should other causes of this harm be taxed/penalized as well? If not, why? For instance, if the harm in question is some people feel varying degrees of worse after using a given product, is there any limit we as a society should set on penalizing the cause of the harm? Should people or entities who say things that make people feel worse be fined/prosecuted by the law? If I feel worse (let's call this 'trauma' or 'anxiety' or 'depression' or 'literally shaking' or 'panic attack') after reading a book or reading a news site, should I have standing to sue the creators and medium which presents said content?