Laws against Holocaust denial

Holocaust denial is illegal in a number of European countries. In addition, the European Union has issued a directive to combat racism and xenophobia, which makes provision for member states criminalising Holocaust denial, with a maximum prison sentence of between one and three years.
Also, the Council of Europe's 2003 Additional Protocol to the Convention on Cyber Crime, concerning the prosecution of acts of a racist and xenophobic nature committed through computer systems includes an article entitled Denial, gross minimisation, approval or justification of genocide or crimes against humanity, although this does not have the status of law.

Of the countries that ban Holocaust denial, a number (Austria, Germany, Hungary, and Romania) were among the perpetrators of the Holocaust, and many of these also ban other elements associated with Nazism, such as Nazi symbols

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Why not for such cartoonists, such laws apply ?