Actually, I was (am) a Jew who searched extensively, looked at Islam quite a bit and while praying in --- of all places --- Saudi Arabia (during the first gulf war) came to know and accept Christ.
I am sorry I offended your friend, but Islam is internally inconsistent. It is clearly just grafted together nonsense.
My point was not that my friend would be offended, but that my friend does not find Islam to be as nonsensical as you do. He know his religion better than any outsider, and he undoubtedly has good reasons to follow it.
In general, I am reluctant to brand any religious beliefs as "internally inconsistent" or "nonsense", especially when I see that many intelligent and well educated people believe in it. Moreover, I would rather learn about a religion from its adherents rather than its opponents. (One would not expect a Nazi to give a fair account of Judaism, for example.)