Should it be illegal to deny man-made climate change?

It's already against the law in many countries to deny the Holocaust, why not climate change? How important is free speech in regards to controlling the way people use energy?
Update: Holocaust denial is illegal in most of Europe, so the framework already exists to criminalize climate-change denial.
Update 2: regarding free speech being an important right: how important? Important enough for people to die for?
Update 3: dang, nobody is biting today!
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