The murder of Theo van Gogh and subsequent threats against other artists, authors, etc. are terrible acts. No one should be killed for such expression.
But I have to say - I find any "juvenile attempt to troll a religious group," well, juvenile and trollish. It is uncivil and rude. It promotes division and distrust, and actively destroys the work many have put into creating safe atmospheres of expression and mutual respect by ridiculing a religious community.
I am not a Muslim. The closest affiliation I'd claim might be with some liberal emerging christianities. But I believe in respecting others enough not to make fun of deeply-held beliefs, which I myself do not hold and which do not impact my life but are absolutely central to the worldviews and spirituality of a very signification portion of the world's citizens.
I'd suggest that "valuing free speech and reason" needn't involve encouraging socially destructive behavior intent on marginalizing a people group, self-selected or not.