Very true and Bill Warner's video shows how Islam attacked the Byzantine empire economy. They didn't just attack the Byzantine's. All of Europe's trade became nearly none existent which created such a dismal life for people in Europe and why we call it the dark ages.
Islam still uses the same tactic today because that was Mo's mode of Operation as a bandit and chief.
Islam and its raiders/pirates basically destroyed trade in the Med. But to claim that this in and of itself destroyed all trade across Europe seems a bit of a stretch. Riverborne and land routes were still available, if a lot more expensive.
During the period in question, the Vikings were ravaging north and west Europe, the Saracens were attacking from the South, and the Magyars were attacking from the East.
Each of these groups penetrated so far into the Continent that it brings up the possibility of their actually bumping into each other. In fact, it's probable, since we know some of the Viking raids penetrated into the Med.
Magyar raids penetrated into central Spain, western France, and southern Italy. They really got around. http://en.wikipedia.org/wiki/File:Kalandozasok.jpg
IOW, the decline of trade and civilization was not due solely or even necessarily to Islamic aggression.
Quite literally the simultaneous persecution of heretics by the Byzantines against the Ghassanids and the Persians against the southernmost tribes in their territories opened the highway to Islam. The loot to be gotten did the rest. The Ghassanids simply switched horses.
Islam would today be an obscure tribal religion based solely in the Saudi peninsula, but for Christian persecution.