According to document 6, why does the governor want to avoid war with mexico

According to document 7, a U.S. Governor, wants to avoid war with Mexico by addressing possible consequences of the Mexican War to the president stating: "Oh Mr. President, if hell itself could yawn and vomit up its (insides) it would plunge the North and the South of the United States into a civil war". The Governor suggests that the U.S. should abandon all ideas of acquiring further territory and that The U.S government should cease the war immediately. He further suggests the army should be recalled and wash Mexican blood from our hands, and swear to preserve honorable peace with all the world and eternal brotherhood with each other.