Allowing Allah and his apostle to speak for themselves is the most damaging thing one can do to Islam.
The Catholic Encyclopedia does a good job of highlighting some of the issues all but Muslim males should (or will) have with the doctrine of Mahomet (and this in an article from 1910!).
Note the echoes of Manuel Palaeologus II, quoted by Pope Benedict:
Quoting Johnstone, Zwemer concludes by remarking that the judgment of these modern scholars, however harsh, rests on evidence which "comes all from the lips and the pens of his own devoted adherents . . . And the followers of the prophet can scarcely complain if, even on such evidence, the verdict of history goes against him".
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What is really good in Mohammedan ethics is either commonplace or borrowed from some other religions, whereas what is characteristic is nearly always imperfect or wicked.
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In matters political Islam is a system of despotism at home and aggression abroad. The Prophet commanded absolute submission to the imâm. In no case was the sword to be raised against him. The rights of non-Moslem subjects are of the vaguest and most limited kind, and a religious war is a sacred duty whenever there is a chance of success against the "Infidel". Medieval and modern Mohammedan, especially Turkish, persecutions of both Jews and Christians are perhaps the best illustration of this fanatical religious and political spirit.