Denial

In the countries of Austria and Germany, Holocaust denial is a crime punishable by imprisonment.

While Holocaust deniers insist they are bona fide historians, some of their most prominent representatives have been shown in court to have a pattern of falsifying historical documents (e.g.David Irving) or deliberately misrepresenting historical data (e.g.Ernst Zündel). This history of Holocaust deniers distorting, ignoring, or misusing historical records has led to almost universal condemnation of the techniques and conclusions of Holocaust denial, with organizations such as the American Historical Association, the largest society of historians in the United States, stating that Holocaust denial is "at best, a form of academic fraud."
(Wikipedia)

Now why can't we make global warming denial a crime?