In regards to the first Crusade, the participation of the "ignorant pesentry"(sic) as you put it, was not so much a planned response by the Pope as it was a grassroots response among the poor who followed such charismatic leaders as Peter the Hermit.
It seems you would lump such a response in with the actions of Bin Laden's modern day followers. I would disagree with you for several reasons.
1. Peter's followers were "ignorant pesents" who were at the mercy of the Church and were (for the most part) leading miserable exsistences. They didn't read or write their own tongue, not to mention Latin. They understood little to nothing about such subjects as history, politics, or geography. The leaders of Al Quiada find willing volunteers among a broad base of followers, some who have college level educations!
2. The call by such men as Peter appealed to the "pesents" spiritually, as you implied. True! The same appeal does exsist among today's impoverished Islamic suicide bombers who seek to advance their religion. But look at the motivations of the leadership! The Pope's appeal was directed at the WARRIOR caste in hope that they would re-direct their substantial internal warring and fighting into something less destructive domestically and perhaps into something beneficial to the Byzantine lords who were being challenged on their borders. The MILITARY troops which responded to the Pope's request succeeded in their goal of seizing Jerusalem and making the way safe for Christians making pilgrimages to the Holy Land. The "pesents" failed and were quickly destroyed by Muslims soon after departing Constantinople. Do you REALLY think Peter the Hermit had a CLUE when he led them to this slaughter? No! Was Peter acting under the direction of the Pope? No! Do you think the leaders of Al Quiada know what they are doing when they manipulate the ignorant? Of course they do.
3. The purpose of the Crusades was not the eradication of Islam. The objective of Al Quiada and a dozen or more Muslim groups is the COMPLETE destruction of Israel and the Jewish people therein.
There is a distinction.