First off, may I just say that I do not believe that the crusades were Christian or at the least justifiable. But ever since 600AD, the Muslims began slaughtering and overrunning Christians in Egypt, Palestine, Asia Minor and even Spain. Almost 2/3 of Christian lands had been conquered by the Muslims and they were no preparing to invade the mainland. Another misconception is that the Christians were taken care of on their pilgrimages, but the opposite is true. Over 30,000 churches had been burned down and over 3000 christians had been murdered in Jerusalem. The Crusades were an act of defense long overdue.
I have a few points to make.
1) No act of 'self defense' can involve 30,000 soldiers marching across the world to go to war. Maybe it's retaliatory, but its not self defense.
2) Your facts are fundamentally incorrect. The pilgrims killed by Muslims in Egypt and the Near East were, quite often violent and antagonistic towards Muslims. Also, the type of Islam prominent at the time specifically forbade the burning/desecration of the holy places of other faiths.
3) Saying those lands were Christian is incredibly hypocritical. Not only was Christianity not the original faith in that area, but Christains had 'conquered' those same lands not a thousand years earlier. The taking of Christian lands by Muslims is a repeat of Christians doing the very same thing to whoever had been there first.