This is not what the text says

in reference to:

"the document encourages Christian and Muslim preachers to say only things about the other religion that are well received by their neighbours and colleagues from it. This principle appears to suggest that no Christian critique of Islam can ever be legitimate, and might even be seen by some as an implicit acceptance of dhimmi status, which forbids non-Muslims to do anything objectionable to Muslims."

The text referred to actually talks about not saying things that the other would not recognise. It is phrased in such a way as to allow critical comment but to disallow or discourage unfair criticism. So it would allow Muslims to say that Christian religion has been used to justify morally repugnant acts in the Crusades, however, it should discourage them from making the accusation that the doctrine of the Trinity is polytheism. Far from a reproduction of the conditions for a cowed dhimmitude it is actually a call to truth-telling and the discipline of neighbour love: to do to the other what we would have them do to us; in this case to speak fairly and charitably. I fear that this bit of the statement is in danger of failing that test.

- Barnabas Fund - hope and aid for the Persecuted Church | Persecuted Christians : Recent Changes in Christian Approaches to Islam (view on Google Sidewiki)