Hobbes is an idiot and not fun to read at all. He's only relevant if you want someone who's advocating for totalitarian government over the individual, which I don't think is a place you want to go with the essay. I would avoid contractualism, its somewhat silly.
A more modern liberal philosopher (in the same line of thought as John Stuart Mills) would be John Rawls, though I'm not entirely sure if he touches on the subject of free speech explicitly (I'm sure he must).
If you want to expand the essay in interesting ways (and bring it into the 20th century) you can look into some of Herbert Marcuse's writings on freedom and the
way freedom of speech is used in modern society. You'd probably find "An Essay on Liberation" and the chapter "New Forms of Control" in One-Dimensional Man useful. More generally, the Frankfurt School of philosophers deal with the issue often. A great source would be Jurgen Habermas, who deals with the idea of an ethical community constantly (which he bases on the idea of communication). You could try "The Inclusion of the Other" which is definitely available online. Here's one excerpt:
U like Nercuse a lot dont you^^ id stay with habermas, fokus on his concepts of hermneutics thou ^^
