Islam hasn't always been puritanical . . .
In addition to learning of Sayyid Qutb's position as a bridge between the Muslim Brotherhood and Wahhabi Islam, I learned something else intriguing from reading Samuel Helfont's monograph, this time concerning the Wahhabist assualt on Ottoman Mecca, a place that hardly differed from any secular 'sin-city' at the turn of the 19th century:
Even more revealing of Wahhabism were conflicts in the first decade of the 19th century with the Ottomans in the holy cities of Mecca and Medina. The Wahhabists made drastic changes, many of which were intended to expose the faults of Ottoman Islam. Wahhabists criticized orthodox Ottoman theology and Sufi practices and faulted the Ottomans for failing to implement even the more lenient interpretations of Islamic law. As one historian explains, "The status of the holy city [Mecca] made its inhabitants feel superior to all other Muslims and led them to excuse a certain lewdness of behavior. Whole blocks of Mecca had belonged to prostitutes, who even paid a tax on their occupation. Homosexuality was widespread. Alcohol was sold almost at the gate of the Kaaba and drunkenness was not uncommon." (Samuel Helfont, The Sunni Divide: Understanding Politics and Terrorism in the Arab Middle East, page 6)This account of Mecca is hard to imagine today, but I see where the Wahhabi Muslims' puritanical impulse originates, for they criticized the Ottomans for being so little Muslim that "even the more lenient interpretations of Islamic law" were neglected in favor of purely 'infidel' practices -- such as trafficking in alcohol and sex -- and Wahhabists have thus had to maintain purity ever since or lose their legitimacy entirely.
 Esther Peskes and W. Ende, s.v. "Wahhabiyya," in Encyclopedia of Islam, eds. P. Bearman, C. E. Bosworth, E. van Donzel, W. P. Heinrichs, and Th. Bianquis (Leiden: Brill Online, 2006), Volume XI.
 James Wynbrandt, A Brief History of Saudi Arabia (New York: Checkmark Books, 2004), p. 136.
The Wahhabists in power have therefore had far less interest in implementing "even the more lenient interpretations of Islamic law" than did the Ottomans, albeit with an opposite result -- rigor over neglect.