The Catholics? Yes good point, it most certainly was the Catholics who stabbed their fellow Christians in the back and after an ogry of bloodletting and theft in Constantinople left the city so weakened that the Ottomans were able to finally conquer it. Glad to see you supporting some actual history for once.
Then you have the massacre of the Latins in 1182. 80k killed by Andronikos Komnenos.
Anyway you slice it the Venetians and the Latins had a casus belli.
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