Hello! I have a few ideas and can help answer your question,
I would recommend reading up on Kant ethics before pursuing that route. Kant contradicts himself at points, but used effectively and wisely, can be good. My value for Aff is Democracy and my criterion is along the lines of constitutionalism. As the other two have said, go with constitutionality or something of the sort, but make sure to have a good defense for it (like, make sure you can explain why we must follow the Constitution or why it's good). As for Neg, my value is Deontological ethics and my criterion is Government legitimacy. Deontology deals with Kant, so as I said read up on him if you choose that route. Other good Neg values are discourse (importance of discourse), structural violence, and justice. A great criterion for Neg would also be the purpose of education.
Fighting words are NOT constitutionally protected, so there is no need to bring them up. This really depends on whether or not you think hate speech is constitutionally protected. For Aff and Neg, I would say yes. If you insist that hate speech isn't protected for Neg, then why are you arguing it? Same goes for Aff. To defend hate speech for Aff (if it comes up, which is highly likely), then state that violent and harmful hate speech is not protected (liability, fighting words, etc). That means you're defending hate speech that doesn't incite violence and is protected.
Another route of defense is by stating that freedom of speech helps minorities (more than hurts). Minorities can choose to respond to hate speech and in instances have used freedom of speech to create change (MLJK, Susan B. Anthony, etc) You can also use the "marketplace of ideas" strategy, which basically states that all speech must be allowed since it helps generate ideas and can help stop bad ones (racism etc). I would research "marketplace of ideas" as a defense
Hope this helps. Good luck!