Dhimmi

Historically speaking, dhimmi (Arabic: ذِمِيّ), a term meaning "protected people," was used to describe non-Muslims living under Islamic rule. Dhimmi status conferred protection and allowed the individual to live peaceably if they met various requirements. Under sharia, the status of dhimmi could originally be conferred only upon "People of the Book," i.e. Christians and Jews. Islamic scholars later expanded it to include religions such as Hinduism, Buddhism, and Zoroastrianism. Dhimmi were exempt from military service and required to pay a tax known as the jizyah.

Nowadays, Islamophobes use the term to refer to useful idiots (mainly white Westerners) who do not realize the threat that sharia poses to liberty, America, and God.

Modern use
The far right has co-opted the term to describe anyone who is not a Muslim, but does as much as possible to undermine Western civilization. People who use this term are generally scared of things like madrassas entering their neighborhoods and mosques being built on the ruins of the World Trade Center.

So potent is this weasel word that it is now part of an entire concept of dhimmitude, with which the right wing is (mostly) unsuccessfully using to try to squelch the Left. The word dhimmitude was claimed to have been coined by islamophobe Bat Ye'or, and was first publicly used by the Christian president of Lebanon, Bashir Gemayel, during the Lebanese Civil War.

Legitimate criticism?
The propensity for an individual to use this term is usually directly proportional to their xenophobia and hatred of Muslims. However, this is no reason not to hear out reasoned criticisms of Islam as articulated by rational folks.

There is much evidence to support the idea that certain Islamic doctrines are particularly opposed to many of the Enlightenment values which made modern science possible, and deserves censure in this regard. These criticisms go against the ideas that Islam puts forth and are not meant as a personal attack on any particular Muslim (as long as they're not a terrorist).

This idea confuses many on both sides of the political spectrum, who ironically share the common stereotype that Muslims are brown. Lefties use this as a wedge for social justice to argue for the oppression of Muslims, while wingnuts are clearly just being racist and use it to fuel their hatred of everything Muslim-related.

At the end of the day, Islam does promote some bad things, but it shouldn't be left to unhinged, hypocritical Christians to attack these things.

List of so-called dhimmis
Every year, the readers of Robert Spencer's blog Jihad Watch nominate a Dhimmi of the Year. Here are some of the candidates and winners of previous years along with other random accusations of of dhimmitude:
 * Michael Bloomberg
 * Barack Obama (when he's not a Muslim)
 * Jimmy Carter (three years running!)
 * Tony Blair
 * Jews (yes, all of them)
 * Jews (yes, all of them)