I don't know where this entry originated, but it is almost dead wrong. There was no love lost among the various groups, but this was Venetian imperialism, pure and simple

This had very little, if anything, to do with religion or intolerance.  The fourth Crusade was effectively hijacked by the Venetians (the Crusaders didn't have the money to pay for passage to the Holy Land) to fight on behalf of a Byzantine prince/usurper.  When the new puppet emperor refused to pay the Ventians and Crusaders for their mercenary services, the Crusaders ran amok and sacked Constantinople, then split up most of the Byzantine empire between themselves and the Venetians.  Religion was basically a pretext for greed and ambition-as it often was in medieval times.