Sorry, Phil, this guy is a pundit playing fast and loose with the facts in order to make his point. Here are a couple of counters:
The Prologue to the Crusades: 500 Years of Muslim Advance
The Crusades can only properly be understood in terms of the 500 years of Muslim advance into the West that preceded them.
Sure, but the 500 years of Muslim aggression can only be properly understood in terms of the previous 800 years of Western aggression that began with Alexander and continued on with the Romans and Byzantines, but that can only properly be understood in terms of the 50 years of Persian aggression during the Greco-Persian Wars.
The East and West have been in near constant conflict for 2,500 years. The Roman-Persian Wars (the Romans being the Romans and the Byzantines, and the Persians being the Parthians and the Sassanids) had been chugging along for nearly 700 years before the Muslims got involved. You can't just pull the Muslim Expansion out of the timeline and claim that it's something different.
Of course, there were sins of overreactions by some Crusaders. But most of these were deeply regretted and forgiveness was sought by Christians who participated in them.
The Fourth Crusade set out in 1202, ostensibly to conquer Egypt. Presumably they had the best intentions, but - somehow or other - they accidentally besieged, conquered, and sacked
Constantinople. Oops. Then they inadvertently crowned one of their guys the new emperor, divvied up the rest of the Byzantine territory among themselves, and called it a conquest.
Regretfully, according to Mr. Geisler.
The result was 50 years of war between Eastern and Western Christians. By the time the Byzantines recaptured their capital the empire barely extended past its walls. They held on for a couple hundred more years - everything took longer back then - but eventually the Ottomans finished them off.
I'm sorry, but calling the deliberate sack of the largest Christian city in the world by the very people who traveled east to protect it (out of the goodness of their hearts and a deep and abiding love for their fellow Christians) a "sin of overreaction" is a bit much.