why does the dutch pirate get angry at gulliver?

Gulliver asks for mercy to be extended to himself and his men. This angers the Dutch pirate beyond reason. We can infer from the text that the pirate did not like Christians.

He observed among them a Dutchman, who seemed to be of some authority, though he was not commander of either ship. He knew us by our countenances to be Englishmen, and jabbering to us in his own language, swore we should be tied back to back and thrown into the sea. I spoken Dutch tolerably well; I told him who we were, and begged him, in consideration of our being Christians and Protestants, of neighbouring countries in strict alliance, that he would move the captains to take some pity on us. This inflamed his rage; he repeated his threatenings, and turning to his companions, spoke with great vehemence in the Japanese language, as I suppose, often using the word Christianos.