What opposing claim does Jefferson anticipate in lines 15-22? What counterargument does he make at the end of this paragraph, and what does he say he is about to do?

when a long train of abuses and usurpations, pursuing invariably the same object, evinces a design to reduce them under absolute despotism, it is their right, it is their duty, to throw off such government, and to provide new guards for their future security.