I can't be sure, because I haven't seen an English translation of the full decision (please let me know if you have one), but here's the report from the NRC Handelsblad newspaper's Web site:
"Stop the tumour that is Islam" is not an insult to a group on the basis of its religion, the Dutch high court ruled on Tuesday. An activist from the southern town of Valkenswaard ... has been acquitted of the charge [of insulting a group on the basis of its religion, the Dutch high court ruled on Tuesday]
The man from Valkenswaard had hung [a] poster after the 2004 murder of Dutch filmmaker Theo van Gogh by a Muslim extremist [that said]: "Stop the tumour that is Islam. Theo has died for us. Who will be next? Resist now! National Alliance, we will not bow down to Allah. Join now." ...
The high court on Tuesday explained its ruling by saying that it is not a crime to express insults towards religion. "Not even if that happens in such a way that the devotees feel their religious feelings are hurt", the court said.
The highest judge in the Netherlands said that only if a needlessly offensive remark is 'explicitly' geared towards a certain group, which is distinct from others in society based on its religion, can there be a matter of group insult as defined in article 137c of the Dutch criminal code. For an insult towards a group to be punishable, that group has to be 'collectively' hit in what defines that group, namely religion. Criticism towards opinions that exist within a group or the behaviour of people belonging to that group cannot be penalized, according to the ruling....
The high court said the same criteria of group insult will apply in the prosecution of Geert Wilders....
Thanks to Religion Clause for the pointer.