When I was a member of the Inter faith Sanctuary, the pagans , and heathens, those who arguably are vanguards of freedom from tyranny, would entertain  various subjects of conversation. Often done on line on a private thread. Occasionally , a member of a armed forces, stationed in DC, (you know where) would engage with us his educated thoughts on various topics. He was/is a PhD in Psychology. I found discussion s with him to get well 'led' , in that I always came away with a good idea.

Remember 'on the Mysteries' , Iamblichus tells us, 'Good means that which is conducive to what we want to achieve.'

Ben, the short answer , is first there is no one panacea to keep us from allowing the freedom of speech, yet there are instances when it needs to be restricted for the benefit of the majority or minority. It could be said that like obscenity, " you will know it when you see it." And yet from our conversations there is a guideline, that  emerged. Here is my version,

Speech and communication, should be free until it violated Tolerance. One, nor We, should ever tolerate, the darkness of Intolerance. I have contemplated this, and found it to be agreeable. 

In keeping with the above concept fellow members, especially those who would also listen to Dead Man's party at Midnight, espoused, and encouraged, 'it is a civic duty, to punch a Nazi.' And to answer Ben's possible doubt, how is this or who should judge. I say ,  I know common decency has been sidelined recently, Critical thinking has become a more rare commodity than it once was.  But this thought has been espoused by others before.  One was the Budha Siddartha. Truth is truth but when we remove Truth from the first cause, it is no longer Truth, and applying this to the problem of allowance  of a given Human right, someone who tries to hide their agenda and misuse a personal freedom , especially those that are harmful to even hearing it, should not be protected by his freedom. Because as they misuse the freedom they lose it by their own actions.  One should never have to tolerate Intolerance. In the old days we had Social consequences. Because , in kart the internet, allows some people to spread misinformation, and they are safe from becoming a Social outcast. They can lie, and go to church and feel justified in what they do by cherry picking religious expressions , albeit, they are expressions but deny the fundamental truth their religion is based upon.

And those most reluctant to have to judge, are the very same who are empowered to do so. There is no one law which governs this as each case or instance must be judged by its own merit. 

May those with ears and eyes hear and see.

Edit: How is society to limit wasted resources, having thousands of such questions tying up our precious resources? Only Education limits the darkness of mind, and creates a sweeping away of our true sins of Racism, Prejudice, Bigotry, especially when it tries to hide in the harbors of Religion or Science. Physician, heal thyself!