Of course there's this problem:
"Bernard Lewis states that the Muslim laity and Islamic authorities have always had great difficulty in accommodating post-Islamic monotheistic religions such as the Bahá'í Faith, since the followers of such religions cannot be dismissed either as benighted heathens, like the polytheists of Asia and the animists of Africa, nor as outdated precursors, like the Jews and Christians. Moreover, their very existence presents a challenge to the Islamic doctrine of the perfection and finality of Muhammad's revelation."
http://en.wikipedia.org/wiki/Bah%C3%A1'%C3%AD_Faith