The issue is that 'danger' is in the eye of the beholder. There are plenty of people who would love to ban advocacy of Socialism or Communism. There are people who want to ban 'hurtful' speech. And people who want to ban 'blasphemous' speech. In the end, they are all self-interested parties who want to ban speech that they disagree with. There is no magic wand that can ban harmful speech without creating a framework for authoritarian meddling, with very few exceptions, which are already on the books.