Arab reformists are constantly threatened by Islamists, who consider freethinkers to be guilty of the worst of crimes.  The most recent death threat against Arab intellectuals was issued by Al-Qaeda leader Osama bin Laden.
In an audiocassette released April 23, 2006, bin Laden addressed the issue of the Danish cartoons and what he regards as the Arab countries' failure to show an appropriate response. He emphasized that anyone mocking the Prophet or making fun of Islam should be killed.
Likewise, bin Laden attacked Arab "freethinkers," several of whom he mentioned by name, and called for them to be killed as well. He cited the precedent of Ka'b ibn Al-Ashraf, whom the Prophet had killed for writing poems against him, as a model for proper conduct in such cases. According to bin Laden, there is no need to consult anyone on this matter; every loyal Muslim should see it as his duty to eliminate these heretics.
The following are excerpts from bin Laden's speech, as posted by the reformist website Middle East Transparent on April 27, 2006. 
Freethinkers and Heretics who Defame Islam Should Be Killed
"To the entire Islamic nation...: This speech comes to further urge you and prompt you to [come to] the aid of the Prophet and punish those responsible for the vile crime being committed by some journalists from amongst the Crusaders and the apostate heretics, who have insulted the Prophet Muhammad…
"Imam Ahmad  said: 'Whoever reviles the Prophet or belittles him, be he Muslim or infidel, should be killed.' The freethinkers and heretics who defame Islam, and mock and scorn our noble Prophet - their case and the law concerning them have been clearly expounded by Imam Ibn Qayyim [Al-Jawziyya].  He made it clear that the crime committed by a freethinker is the worst of crimes, that the damage caused by his staying alive among the Muslims is of the worst kind of damage, that he is to be killed, and that his repentance is not to be accepted...
"Ibn Qayyim Al-Jawziyya said, commenting on [Koran 9:12]: 'Whoever defames our religion is a leader of disbelief.' Many are the leaders of disbelief in our days in the lands of Islam, and many are the followers of Ka'b ibn Al-Ashraf in the Arabian Peninsula.  Many of them are writers in newspapers, and many of them are actors and broadcasters in the media. We warn here that a Muslim is not allowed to listen to any program that includes discussion with heretics, or any show that makes fun of Islam and of religious Muslims, for this is one of the greatest sins.
"How numerous are the heretics who are [government] ministers! And the foremost among them is the minister of labor in the Land of the Two Holy Shrines [i.e. Saudi Arabia], Ghazi Al-Qusaybi. Whoever wants to see the official fatwa proclaiming him guilty of disbelief and apostasy - such a fatwa was issued by former chief mufti 'Abd Al-'Aziz bin Baz, just as he issued a fatwa on the disbelief and apostasy of the heretic Shamlan Al-'Issa in Kuwait. 
"Among these heretics is Ahmad Al-Baghdadi  in Kuwait, and Turki Al-Hamad  in the Land of the Two Holy Shrines - a fatwa concerning the latter was issued by Sheikh Hamud Al-'Uqala - and many others like them. The book Modernity in the Balance of Islam  contains many of their names. Sheikh Sa'id Al-Ghamidi has also warned against them in his audio tapes..."
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Do Not Consult Anyone About the Killing of These Heretics
"Indeed, this is our Prophet's law regarding anyone who mocks him, and belittles Islam and scorns it... They should be killed... Take an example from Muhammad ibn Maslama and his companions [who assassinated the poet Ka'b ibn Al-Ashraf]. It is intolerable and outrageous that the heretics are among us, scorning our religion and our Prophet.
"Therefore, you must fear Allah and do His will. Do not consult anyone about the killing of these heretics. Be secretive in carrying out that which is required of you.
"So much for the apostate heretics."
 See MEMRI Inquiry and Analysis No. 254, "Arab Intellectuals: Under Threat by Islamists," November 23, 2005: Arab Intellectuals: Under Threat by Islamists.
MEMRI Inquiry and Analysis No. 208, "Accusing Muslim Intellectuals of Apostasy," February 18, 2005: Accusing Muslim Intellectuals of Apostasy.
MEMRI Special Dispatch No. 1070, “Saudi Doctorate Encourages the Murder of Arab Intellectuals,” January 12, 2006: Saudi Doctorate Encourages the Murder of Arab Intellectuals.
 http://www.metransparent.com/texts/bin_laden_full_text.htm, April 27, 2006. The only prominent Arabic newspaper to attack bin Laden's threats was the London Arabic-language daily Al-Sharq Al-Awsat in an editorial by its editor-in-chief, Tariq Al-Homayed.
 Ahmad ibn Hanbal (d. 855 CE), a famous traditionist, and author of the well-known hadith collection Musnad Ahmad ibn Handal.
 Muhammad ibn Abu Bakr (d. 1350), known as Ibn Qayyim Al-Jawziyya, was Ibn Taymiyya's most eminent and trusted disciple.
 Ka'b ibn Al-Ashraf was one of the leaders of the Jewish tribe of Abu Nadhir, who was assassinated on Muhammad's orders (probably in 625 CE). According to Islamic sources, he incurred the Prophet's wrath by composing poetry calling to fight him and slandering Muslim women.
 Shamlan Al-'Issa is a political science lecturer at Kuwait University. See MEMRI Special Dispatch No. 224, "The Public Debate on Kuwait's School Curricula: To Teach or Not to Teach Jihad," June 2, 2005, The Public Debate on Kuwait's School Curricula: To Teach or Not to Teach Jihad.
See also MEMRI Special Dispatch No. 242, "In the Arab Press: Criticism and Rejoicing at Hurricane Katrina," September 22, 2005, In the Arab Press: Criticism of Rejoicing at Hurricane Katrina.
 Ahmad Al-Baghdadi is a Kuwaiti intellectual. See MEMRI Special Dispatch No.1070, "Saudi Doctorate Encourages the Murder of Arab Intellectuals," January 12, 2006,
Saudi Doctorate Encourages the Murder of Arab Intellectuals.
 Turki Al-Hamad is a reformist Saudi intellectual.
 This book, written in 1988 by the Saudi fundamentalist preacher 'Awadh Al-Qarni, lists over 200 Arab authors, poets, researchers, philosophers, academics, literary critics, and journalists and accuses them of heresy - thus making their killing licit. See MEMRI Special Dispatch No. 1070, "Saudi Doctorate Encourages the Murder of Arab Intellectuals," January 12, 2006,
Saudi Doctorate Encourages the Murder of Arab Intellectuals.