So I have my own justification for freedom of speech: because we can. Human freedom is important, so we should try to protect it from encroachment wherever possible. With most freedoms — freedom of motion, freedom of exchange, freedom of action — permitting them in full would cause some problems. People shouldn’t be free to walk into other people’s bedrooms, take all their stuff, and then punch the poor victims in the face. But hurling a bunch of epithets at the guy really isn’t so bad.
Freedom of speech is one place where we can draw the line and say: all of this is acceptable. There’s no further logic to it than that; freedom of speech is not an instrumental value. Like all freedom, it’s fundamental, and the only reason we happen to single it out is because it’s more reasonable than all of the others.
Close readers will note that this theory doesn’t quite live up to my own goals. By laying freedom of speech’s provision on top of our reasonable ability to do so, I suggest that freedom of speech could be taken away if providing it became unreasonable. But I think this is the right choice: if people really, seriously started getting hurt because of freedom of speech, it seems right for people to take the privilege away. But, to be honest, I can’t even imagine how that might be possible. Words just don’t genuinely wound, they’re always mediated by our listening.
I do worry that people might try to stretch this justification — say that continued free speech might destroy the war effort, or the government, or civil society. But I have no problem destroying all of those. It’s only the destruction of actual people that I worry about.