Let me try to specify with greater exactness the constituency for militant Islam. It is divisible into three main elements.
The first is the inner core, made up of the likes of Osama bin Laden, the nineteen hijackers, al Qaeda, leaders of the Taliban regime in Afghanistan, and the rest of the network of violent groups inspired by militant Islamic ideology. Such groups have mostly come into existence since 1970, becoming since then an evermore important force in the Muslim world. The network, dubbed the "Islamintern" by some Muslim critics, contains both Shiite and Sunni variants, appeals to rich and poor alike, and is active in such far-flung locations as Afghanistan, Algeria, and Argentina. In 1983 some of its members initiated a campaign of violence against the United States whose greatest triumph so far was the spectacular operation on September 11. In all, the network's adherents are as few as they are fanatical, numbering perhaps in the thousands.
The second ring comprises a much larger population of militants who are sympathetic to al Qaeda's radical utopian vision without themselves being a part of it. Their views were on display daily as soon as hostilities began in Afghan istan: protesters and mujahideen by the tens of thousands, all expressing a determined loathing of the United States and an enthusiasm for further acts of violence. Countries not normally heard from, and hardly hotbeds of radicalism, came to life to protest the U.S. campaign.
As best I can estimate from election data, survey research, anecdotal evidence, and the opinions of informed observers, this Islamist element constitutes some 10 to 15 percent of the total Muslim world population of roughly one billion - that is, some 100 to 150 million persons worldwide.
The third ring consists of Muslims who do not accept the militant Islamic program in all its particulars but do concur with its rank anti-Americanism. This sentiment is found at almost every point along the political spectrum. A secular fascist like Saddam Hussein shares a hatred of the United States with the far leftists of the PKK Kurdish group who in turn share it with an eccentric figure like Muammar Qaddafi. Reliable statistics on opinion in the Muslim world do not exist, but my sense is that one half of the world's Muslims -or some 500 million persons- sympathize more with Osama bin Laden and the Taliban than with the United States. That such a vast multitude hates the United States is sobering indeed.
That is not to say, of course, that anti-Americanism is universal among Muslims, for important bastions of pro-American sentiment do exist. These include the officer corps of the Turkish military, who are the final arbiters of their country's destiny; several leaders of Muslim-majority states in the former Soviet Union; the emerging dissident element in the Islamic Republic of Iran; and, more generally, those Muslims who have experienced at first hand the dominion of militant Islam.

Pipes is by far one of the most important individuals exposing the Islamist threat. His work precedes others by decades. Rarely does he ignore reality and engage in fantasy solutions – like the Oslo appeasement process, which he criticized. Still, I believe he is wrong in his categorization due to some philosophical errors. It doesn’t, however, negate his overwhelming contributions to our understanding of the problem.

Edit (correct typo - thanks Pete)

(Edited by Jason Pappas on 8/07, 7:17pm)