Only tyrants prescribe the writing of history with penal laws.
Whoever argues that peaceful dissidents on historical issues should be deprived of their civil rights for their diverging views, that is: incarcerated, is -– if given the power to implement his intentions -– nothing else but a tyrant (if enacting laws to support his oppressive deeds) or a terrorist (if acting outside the law).
I define as a peaceful dissident someone who does neither advocate, condone, promote, justify or glorify when anyone’s civil rights are being violated. To put it graphically: If anyone advocates the torture of suspects in the war on terror, as has happened frequently in the US, this person has lost the right to complain if getting tortured when falling into the hands of his enemies. Or if anyone justifies the incarceration of people merely due to their religious, political or ethnic affiliation (as has happened to Communists, Gypsies and Jews in Germany, and Germans, Italians and Japanese in the US during WWII), then this person has lost the right to complain if getting incarcerated for being affiliated with a certain school of thought.
Other than that, any event in history must be open to any kind of critical scrutiny. The very basis of all science is that any hypothesis needs thorough testing. Only those hypotheses which can withstand the toughest attempts at refutation can be deemed reliable. Preventing attempts at refutation removes a hypothesis from the realm of science and changes it into a dogma or even a religion. In fact, the very foundation of our humaneness is our ability to doubt, our mental capacity to investigate, and our various skills to communicate. Where doubts, the search for the truth, and our means to tell what we think we have found out are restricted, the very core of our humaneness is being violated; we are intellectually reduced to mere amoebae, as K.R Popper put it.
Being wrong cannot be a reason to punish people, or else we all would be in prison from birth to the coffin. Jesus was wrong, most Jews thought during and after his lifetime. Galileo was wrong, most people of his lifetime thought. George Washington was wrong, most Englishmen thought during the revolutionary wars. Charles Darwin was wrong and his views very upsetting, most people thought in his era. Just because many are emotionally upset by a view deemed wrong does not mean that the view needs to be banned. It may not even be wrong, and the reason why we get upset may lie within ourselves rather than within the view expressed. I suggest this is the case with Holocaust denial/revisionism, too. The more serious revisionist studies are so academically dry and boring, so filled with endless rows of documents quoted from dusty archives that no normal person could get upset by their mere contents. It’s our own mindset which is playing tricks on us, not these works.