History

1. Fortunately, history did not begin when Muhamed was born. For about 500 years before that, the entire Middle East was Christian. After Mohammed, those lands were conquered by Arab Muslims. This explains the Crusades (actually it's a little more complex; the Eastern Church called for help to Rome because the infidels (Muslims) were threatening Constantinople's empire in their continuing conquests, but you get the idea. It was ours; they took it).
2. Thus, under Just War theory -- which, you may have noticed, Islam does not bother with (Islam's Just War Theory is, "you're not Muslim, war is just.") -- the Crusades were a (belated) response to aggression by Islam, and a contemporaneous response to new aggression against the Eastern Church, and threats by the then-Poobah, or whatever they called them, of Jerusalem to destroy the Holy Sepulchre. Of course, measured by the inverse of the Islamic Just War theory ("You're not Christian; war is just."), the Crusades obviously were justified.
3. Many, well, most people are unaware that the Ottoman Empire -- a Muslim Empire, continued to attack deep into Europe into the 1700's, and almost conquered Vienna, Austria in 1683. Muslim aggression against the West has been unceasing for some 1,400 years. And yet, we're the ones always apologizing.