Who argued that imperialism was contrary to the principles of our government?

Mark Twain, along with other anti-imperialist figures, argued that Imperialism was contrary to the principles of American democracy. He believed that the expansionist policies of the United States undermined the values of freedom and self-determination that the nation was founded upon. Twain's opposition was part of a broader Anti-Imperialist League that criticized the moral implications of imperialistic endeavors, particularly in the Philippines.