
Spencer frames his book partly as a testament to the importance of the freedom of speech.

Robert Spencer's The Truth About Muhammad accomplishes Spencer's goal of vilifying Muslims and misinforming readers about Islam. With its lack of analysis, absence of historical context, and gaps in information. Writing in the Asian American Law Journal, Deepika Bains and Aziza Ahmed strongly criticized the book, claiming to find structural problems, as well as "deep substantive flaws", such as unfounded assertions and conclude that: The government of Pakistan confiscated all copies of the book and banned it on 20 December 2006 citing "objectionable material" as the cause. His book is a gift to extremists who can use it to "prove" to those Muslims who have been alienated by events in Palestine, Lebanon and Iraq that the west is incurably hostile to their faith. But the widespread ignorance about Islam in the West makes many vulnerable to Spencer's polemic he is telling them what they are predisposed to hear. People would be offended by an account of Judaism that dwelled exclusively on Joshua's massacres and never mentioned Rabbi Hillel's Golden Rule, or a description of Christianity based on the bellicose Book of Revelation that failed to cite the Sermon on the Mount. There is no mention of Muhammad's non-violent campaign that ended the conflict. He ignores the Koranic emphasis on the primacy of forgiveness and peaceful negotiation: the second the enemy asks for peace, Muslims must lay down their arms and accept any terms offered, however disadvantageous.

When discussing Muhammad's war with Mecca, Spencer never cites the Quran's condemnation of all warfare as an "awesome evil", its prohibition of aggression or its insistence that only self-defence justifies armed conflict. Even more damaging, he deliberately manipulates the evidence. . Consequently he makes basic and bad mistakes of fact. Spencer makes no attempt to explain the historical, political, economic and spiritual circumstances of 7th-century Arabia, without which it is impossible to understand the complexities of Muhammad's life. Like any book written in hatred, new work is a depressing read. The liberal Christian biographer of Muhammad Karen Armstrong criticized the book as follows:

In the book Spencer presents an account of what the Islamic prophet Muhammad said and did from the writings of the early biographers of Muhammad such as Ibn Ishaq, Ibn Sa'd al-Baghdadi, and Muhammad ibn Jarir al-Tabari, as well as the Qur'an and the hadith collections of Bukhari and Muslim. It was published in 2006 by Regnery Publishing. The Truth About Muhammad: Founder of the World's Most Intolerant Religion is a book by Robert Spencer of Jihad Watch and Stop Islamization of America.
