I recently gave a talk about Islam to a church group - for two reasons, I suppose: 1) because it's a contemporary subject which deserves some attention, not least because most news coverage is negative; and 2) because I believe it is a Christian responsibility to listen to others; after all, Jesus practised such hospitality that he would welcome even the people who were feared and avoided by most others. And the responses were interesting! Most were fascinated; they appreciated the need to understand better the religious tradition of Muslims. But someone thought I was "preaching Islam" - I'm not sure how, because I kept emphasising that we have differences, even as we also considered some of the interesting areas of overlap (e.g. Jesus is deeply respected in the Qur'an as a Great Prophet and a revelation of peace.)
Of course, it is always risky for someone of one faith to describe the beliefs of another faith - we can't help but over-simplify things and see them through our own eyes. But it's still important to try to understand where different people are coming from, just as the ecumenical movement has helped different church traditions to understand each other better. It is possible, too, to stand up for what you believe in while also listening to what others say. And in some respects, it is essential.