It would be hard to imagine a place more remote from the violence and turmoil of the Middle East than this quiet cul-de-sac in the southern suburbs of Los Angeles. But as David Sultan opens the front door of his home he glances up and down the street anxiously.

He has good reason to be nervous: ever since Dr Wafa Sultan, his wife, appeared on Al-Jazeera, the Arabic television network, last summer she has been receiving death threats. During that and a second broadcast in February Dr Sultan, who was brought up as a Muslim in Syria, denounced the teachings and practice of Islam as “barbaric” and “medieval”.

“The clash we are witnessing around the world is not a clash of religions, or a clash of civilisations,” the impassioned 47-year-old told Al-Jazeera’s stunned audience across the Arab world. “It is a clash between civilisation and backwardness, between the civilised and the primitive, between barbarity and rationality. It is a clash between human rights on the one hand and the violation of these rights on the other, between those who treat women like beasts and those who treat them like human beings.”

The broadcasts have caused an unholy stir in the Muslim world and virtually overnight have turned Sultan, previously known only to a few for her writings on www.annaqed.com, a small Arab-American website, into one of the most controversial figures in the international debate about Islam. The broadcasts have been downloaded more than 1m times from the internet and she has been interviewed on CNN and profiled by The New York Times and Le Monde.

While some acclaim her as “a voice of reason” others have denounced her as a “heretic” and insist that she deserves to die. What seems to have most infuriated many Muslims were Sultan’s comparisons between how Jews and Muslims have coped with the tragedies that have befallen them.

“The Jews have come from tragedy and forced the world to respect them,” she said, “with their knowledge, not with their terror; with their work, not with their crying and yelling.

“We have not seen a single Jew blow himself up in a German restaurant. We have not seen a single Jew destroy a church. We have not seen a single Jew protest by killing people. Only the Muslims defend their beliefs by burning down churches, killing people and destroying embassies. The Muslims must ask themselves what they can do for humankind, before they demand that humankind respect them.”

Sitting in the airy living room of the spacious modern home where Sultan and her husband live, it is hard to believe this small, neatly dressed woman could be at the centre of an international firestorm. Just as improbable is that the most important and controversial critics of Islamic fundamentalism, violence and intolerance are, like Sultan, women, mostly from Islamic countries.

They include Ayaan Hirsi Ali, the Somali-born Dutch politician, who has strongly criticised Islamic attitudes towards women and the widespread practice of female circumcision in Muslim north Africa; Irshad Manji, a Canadian lesbian of Pakistani descent, whose book The Trouble with Islam Today chastises Islam for its aggression towards women and for its anti-semitism; Amina Wadud, an African-American convert to Islam and Muslim academic and author, who has infuriated traditional Muslims by leading Friday prayer for Muslims in New York, a role traditionally taken only by male imams.

Other Muslim women in the front lines of the clash with Islamic governments are as diverse as Mukhtar Mai, the Pakistani village woman who was brutally gang-raped in 2002 as reprisal for an alleged transgression by her 14-year-old brother, and Shirin Ebadi, the Iranian lawyer who was awarded the Nobel peace prize in 2003 for her defence of the rights of women and children in fundamentalist Muslim Iran.

Death threats against these women are commonplace. Irshad Manji has had to install bullet-proof windows in her home. Ayaan Hirsi Ali has to travel everywhere with bodyguards after the threats against her and the death the film maker Theo van Gogh, her friend and collaborator.

Sultan never imagined her life would take this path. She was born to a large middle-class family in the Syrian port city of Banias. Her father was a grain trader, her mother a housewife. She has nine brothers and sisters. The family was devoutly Muslim and Sultan, who studied medicine at the University of Aleppo in Damascus, says she never had any reason to doubt her faith. But in 1979, when she was a student, she witnessed a horrifying crime. As she stood chatting with some other students on the university courtyard, armed members of the Muslim Brotherhood began shooting at one of her teachers, killing him on the spot.

“They filled his body with bullets as they shouted ‘Allahu akbar! Allahu akbar! (God is greatest!)’,” she recalls. She says they killed him because he was an Alawite, a member of the same Muslim sect as the Syrian president Hafez al-Assad, whom they wanted to overthrow, even though he had nothing to do with politics.