By all means, let us remember the Crusades.
Where shall we begin our rememberance?
How about with the Muslim conquest of Jerusalem, a city holy to the Christian and Jewish faiths?
And now let us pause for a minute to contemplate the outcry that would rise up, if Christians or Jews were to conquer Mecca, a Muslim holy city. The world would never hear the end of it. Violent asshats and useful idiots everywhere would perpetrate and justify all kinds of atrocities because of it.
But the Crusades didn't actually start over the Muslim conquest of Jerusalem.
How about we begin by remembering the letter written by the ruler of Constantinople, a predominantly Christian city and a center of arts, science and culture in the region? The letter I'm referring to was written after Muslim armies besieged the city. The ruler of Constantinople wrote to his spiritual brother, the Pope, pleading for him to raise an army of fellow Christians in Europe, who would relieve his city and aid in its defense.
And now let us pause to reflect that the first Crusade, launched in response to this letter, was an act of defense against Muslim aggression.
Of course, we must also pause to reflect that, to their shame, these first Crusaders got sidetracked along the way, and spent more time looting and pillaging their own countrymen--and persecuting Jews--than they did actually defending Constantinople.
But then we must remember the rest of the history of the Crusades:
Over several hundred years, Crusaders managed to invade, conquer, and rule small scraps of the "holy land" for brief periods of time. They even managed to install a Christian, European king in Jerusalem for a few years, before the Muslims drove them out for good.
In the end, none of the Crusades were particularly successful, and after a couple centuries and many attempts, the European Christians gave up.
There are some valuable lessons that can be learned from this rememberance, and from further study of the Crusades:
First, as I have already pointed out, the Crusades were acts of defense against aggression: Both specific acts of aggression like the Muslim siege of Constantinople, and general acts of religious oppression such as the Muslim investment of the Judeo-Christian holy city of Jerusalem. I, for one, do not begrudge the European Christians their desire to recover their holy city, any more than I begrudge middle-eastern Muslims their proprietary attitude towards Mecca. But, like the Crusaders of old, I do begrudge them their proprietary attitude towards Jerusalem (though obviously I'm not advocating Yet Another Crusade to solve that particular problem).
Second, the Crusades were a failure. The Crusaders lost. They lost because of lack of focus, lack of commitment, internal power struggles, and a number of other reasons--including Muslim military prowess. Far from being a humiliating defeat for the forces of Islam, the Crusades were a great and glorious triumph for the servants of Allah. Arguably, it was their last such victory.
Third, the people of Europe began to prosper, as the Crusades faltered and failed. The Europeans turned to other pursuits. Thanks in part to the diligent work of Christian monks during the Dark Ages, who preserved vast treasuries of knowledge and philosophy, the Europeans were able to build on the foundations of classical civilization--the same civilization that the Arab and Muslim cultures had played a part in creating. This new effort by the Europeans resulted in the Enlightenment: New forms of art and architecture, the scientific method, the differential calculus, and all the good things that have come of these European developments.
Fourth, that while the Crusades were not shining examples of human kindness and justice, they are hundreds of years in the past. Since then, every civilizational advance that today's affluent, educated, middle-class disgruntled jihadi enjoys was produced by European civilization. For this reason I suspect that the real reason the Muslim world cites the Crusades as an example of European injustice is not because it was unjust for the Christians to want to fight for their holy city (which is not actually an unjust sentiment), nor because it was unjust for the Christians to lose that battle (since it's not actually unjust to have your ass handed to you in a war you signed up for in the first place), but because Muslims can't shake the feeling that it's somehow unfair that after winning the Crusades and controlling their enemies' holy city, Arab and Muslim civilization has still failed the test of time. It just doesn't seem fair, does it, that Arab culture hasn't contributed anything much to civilization since they introduced the concept of zero.
In summary: the Crusades were a defensive response to Muslim aggression. The Christians lost. The Muslim world hasn't had a significant victory, nor made a significant contribution to civilization, since.
By all means, let us remember that