I was recently getting my car worked on at the local dealership and, while waiting, ended up watching some of Fox News. Unlike many people, Fox News does not bother me most of the time; if anything, I view it as the anti-MSNBC. In other words, I recognize that it has a specific editorial bent and watch it with that in mind.
On that particular day, they were covering the recent protests in Egypt and specifically addressing their concerns regarding the possibility that the Mubarak regime would be replaced by the Muslim Brotherhood. With little context other than the repeated use of the phrase "Muslim" Brotherhood expressed in a dark and sinister tone, anyone whose knowledge of the world was garnered only from Fox News (and I know more than a few) would automatically infer that this was bad and therefore to be avoided. Another inferred suggestion was that the US should instead support the Mubarak regime at all costs because it was secular and not based on Islam (not to mention his support of a peace treaty with Israel).
But it is this directly implied reference to the negative aspects of Islam (via the twisted ideology of Islamist fanaticism) with the very term of "Muslim" that provokes a sad reminder of the past - one that has been oft-repeated and still is not learned from. Or, more precisely, it has not been learned from in the context of preventing it from recurring. Unfortunately, those who have learned from it have discerned that it continues to work in spite of its negative historical precedents. The lesson, of course, is that in order to foster a willingness to fight against an enemy, it is vitally important to demonize that enemy. And when I say demonize, I mean to classify your enemy as being less than human, as being not worth consideration or insignificant, as being nothing more than an object to be destroyed. After all, it is always far easier to kill someone when you do not consider them to be human or worth the effort to consider why you should not kill them on someone else's orders. And such a demonization can be done based on ethnicity, gender, political affiliation, religion, national standard, or any other subjective measure; there are no limits to this classification.
The historical precedents within just the last century are staggering when we consider that they still continue today. Hitler and his rabid persecution of the Jews during the 1930's and 40's are perhaps the clearest example - but not the only ones. We also have the persecution of Tutsis by Hutus in Rwanda in 1994, the massacres of Kosovars by Serbians in the mid 1990's, the slaughter of Chinese, Koreans and other Asians by the Japanese during WWII and the attacks against civilians (perceived to be enemy supporters) in Vietnam by the United States in the 1960's. This does not include other events that could be similarly classified - China during the Cultural Revolution, the Bolshevik Revolution in Russia, the reign of the Khmer Rouge in Cambodia, nor incidents that occurred under Western colonial rule throughout Africa, Asia and the Middle East.
The key factor that all of those times mentioned above have in common is the consistent dehumanization that took place prior to and during each of them. The view that your enemies were lesser than you whether by virtue of color, culture, religion or political bent was the key factor in energizing the supporters of a given leader to be willing to attack, hurt and kill the "enemy". It is easy to want to destroy something that you do not understand - I have an abhorrent hatred of cockroaches and would sooner kill one than look at it and I do have a general understanding of cockroaches. When your enemies are designated as cockroaches, you no longer see them as human and have less compunction about hurting them (this example is particular to 1994 Rwanda and the treatment of the Tutsis). This is reinforced by ensuring a clear separation and delineation of your enemies (such as the Jews in Germany who were forced to identify themselves as such by the wearing of a yellow star) and making certain there is no mixing that might lead to a recognition that your opponents are very similar to yourself. Referring to your enemy in negative stereotypes and not understanding their point of view (the US attitude toward its enemies in Vietnam as well as the Japanese during World War II) leads to an unbridled arrogance that is hard to overcome and bridge the gaps between.
Yet the one way to overcome this sort of demonization is to open the lines of communication between various groups and allow people to be more than just a stereotype. When your only understanding of someone different from you is a stereotype, then it is not difficult to carry that image into a negative portrayal that can easily be twisted into something that inevitably becomes far more dangerous. But the responsibility for breaking through the barriers separating groups lies with everyone - not on the other people. Indeed, when it relies on other people, that is where the path toward demonization begins. Find someone who is different and learn how to prevent those barriers from being erected in the first place.
(Special thanks to FP for editing assistance. Any errors are mine alone.)