Here are a few suggested books for you. You'll find many more in the Library Catalog.
The Case Against Free Speech: The First Amendment, Fascism, and the Future of Dissent by 
Free Speech in the Digital Age by 
Free Speech: Ten Principles for a Connected World by 
Freedom of Speech: Mightier Than the Sword by 
Kent State: Death and Dissent in the Long Sixties by 
Gitlow V. New York: Every Idea an Incitement by 
The Great Dissent: How Oliver Wendell Holmes Changed His Mind -- and Changed the History of Free Speech in America by 
Muzzled: The Assault on Honest Debate by 
Shame Nation: The Global Epidemic of Online Hate by 
What Snowflakes Get Right: Free Speech, Truth, and Equality on Campus by 
