Answer: D. . . . they do not rashly engage in war, unless it be either to defend themselves or their friends from any unjust aggressors, or, out of good nature . . .
This sentence summarizes the main idea of the passage. The people More is describing do not engage in war, except for a few exceptions. They believe war to be brutal and the victory inglorious. The only exceptions in which they believe war might be justified are to defend themselves or their friends, or to help those who are oppressed.
