The Free Speech Debate project has a website at which you can look at its 10 draft principles. Principle 4 - 'We speak openly and with civility about all kinds of human difference' - is discussed in posts by Jeremy Waldron and Ivan Hare, who argue respectively for and against laws prohibiting hate speech. For Waldron, hate speech constitutes a harm, attacking as it does the dignity of those it targets; for Hare, legal prohibition of hate speech 'damages our fundamental rights and undermines the openness of public discourse'.
I'm with Hare on this. I'll give just one reason why. Preventing harm to others is a proper object of legislation, but the harm needs to be clearly specifiable. Thus, physical violence or the direct incitement to it leave no doubt about the nature of what is being prevented. But harms to dignity that are contained only in certain words, whether written or spoken, is more nebulous. How much has to be said and how bad does it need to be before it amounts to an attack on someone else's dignity? The term 'hate speech' suggests something pretty fierce. But what about the casual slur, the insult between the lines, the vague innuendo? Speech is the subtlest of instruments, and verbal indignities can be visited upon others in multiple ways, from the most brutal to the very mild. Offence can be taken for small slights as well as for hateful lies. It is not clear to me how the law is to determine the proper scope of verbal harms to dignity. In that situation the old principle of keeping the freedom to say what one believes as extensive as possible should be upheld.