At a time when conflict is already lethal and interreligious understanding is more urgently needed than ever, some might argue that we should gloss over the points of difference. I agree about the need for interreligious understanding; I disagree about the recipe for achieving it.
I suspect that people who have made such statements doubting that Islam is a religion often do have knowledge and a real conception of what a religion is and they are able to listen to a discourse if it is respectful.
In our studies of Christianity, Judaism and Islam, one thing has been particularly striking: the exclusivism of the Abrahamic religions. Jews are the "chosen people," the path of Jesus is the "only way" and Muhammad's was the "final revelation."
The significance of such an approach to dialogues is not dependent upon whether both sides agree or disagree on a given issue; rather, that we are comfortable accepting these differences as a starting point.