You should read both the article and the comments.
I could be wrong, but my hunch is that Zuckerman is probably right. Also, I don’t know this for a fact either, but I suspect that the same fear which stifles atheist criticism of Islam also stifles Christian criticism of Islam. Yes, there are atheist and Christian critics of Islam, but it seems very easy to believe that there are less critics than there would have been if Islam did not have the kind of reputation it does.
What do you think?