I have long noted that Muslim reform attempts are consistently stymied by declarations from the mujahedin — supported by Qur’an and Sunnah — that the reformers are contravening the tenets of true Islam. These declarations, of course, are often backed up by murderous threats, in accord with the traditional Islamic death penalty for apostates and heretics.
Here is a prime example: “Arab Reformists Under Threat by Islamists: Bin Laden Urges Killing of ‘Freethinkers,'” from MEMRI, with thanks to DFS:
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….
“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.”
Ka’b ibn Al-Ashraf was a poet. The Muslim Prophet Muhammad asked for his death after the poet insulted him. It is interesting to note that when I point out that Muhammad ordered the assassination of his enemies, I am reviled as an “Islamophobe.” But Osama, you know, doesn’t read my books. He reads the Islamic sources, and he takes for granted that his Muslim audience reads them too, and knows that what he says his true. That’s why his appeal has power in the Islamic world.