My personal experience is that I arrived to my practice of the Buddhadhamma via Sufism, because of what I see as their "essential" teachings. Of course I am not referring to what most call "Buddhism", or the Arab nationalism most call "Islam". I am speaking to the "essence" of both, which reaches beyond the organized, institutionalized, dogmatic traditions.
I have practiced [and continue to practice] Islam for quite some time and see absolutely no conflict between either dhamma. While on retreat I participated in a dhamma discussion on "touching the roots of our western traditions", which included talks on how practitioners of Christianity, Judaism and Islam could resolve their practice of the Buddhadhamma alongside the spiritual traditions passed on to them from their ancestors. Thinking that we must do it "this way" or that way" is very much the product of dichotomous thinking and attachment to dualism.
I have been told by my teacher that the practice of the Buddhadhamma will, in fact, strengthen the practice of whatever spiritual tradition you practice because it allows you to get to the root/essence of the tradition. I find this to be very true.
Those who can see the similarities of Christianity and the Buddhadhamma, but cannot do so with Islam are falling into a dogmatic, clinging trap. Judaism, Christiantity, and Islam are all Abrahamic/Semitic traditions and essentially teach the same principles. The practices often differ, but that holds true for so-called Buddhism as well, or we would not feel a need to divide a forum into Theravada, Hinayana, Mahayana, Vajrayana, etc.
Islam has a practice called Zhikr, which is essentially the practice of mindfulness and can also be directly related to vipassana. When reciting the Quran, paying attention to the various pauses indicated by punctuation marks, one is engaging in a form of "fully aware breathing" prescribed by Shakyamuni Buddha in the Anapanasati sutra. Compassion IS Rahman, and zakat is charity, these are also commonalities they share. If we put our minds to it we could probably point out other similarities.
There are many ways to describe and approach reality, the idea that any tradition or spiritual practice is the ONLY way is somewhat ludicrous [my attempt to be polite because it is totally ludicrous!
]. So, if we allow ourselves to get past the disturbing emotions or cognitive obscuration we have attached to any particular dhamma that we do not see as our own, I really don't see why we cannot discuss ANY topic and maintain decorum.