Found this note from the Dean of the Boston School of Public Health on when you need to restrict speech so that you can actually have a free exchange of ideas in an academic context. Very insightful.
He lists three valid reasons to block speech in a public arena, so that all voices can be heard:
1) We have no obligation to provide a platform to speech that is not open to responses and rebuttal.
2) We can curtail speech that endorses or incites violence.
3) Academic speech can be limited when it traffics in well-established falsehoods.
His argument for the last point draws a careful line between controversial speech and promoting known falsehoods.
