Distrust of any aggressor by a nation inclined toward peace.
Disgust at the "scrap of paper" episode.
Resentment at the invasion of Belgium.
Contempt for the Imperial Government which is industriously screwing the last penny of "indemnity" out of a ruined nation, which the people of the United States are taxing their private means to keep from starvation.
Further back there are other reasons.
For thirty years the press of Germany has seldom missed an opportunity to express its contempt for Americans. Any American who has ever lived in Germany or who has read German newspapers during the last thirty years is aware of the tone of the German press concerning America and Americans. No innuendoes have been too vulgar, no sneers too brutal for the editors of these papers, and, presumably for the readers.
Also Americans do not forget the attitude of the Imperial Government during the Spanish war. The bad manners of a German Admiral are bearing fruit.
Imperialism we Americans do not understand, but it need not make us unfriendly to empires.
But we do understand when manners are bad, or when a military caste, which maintains its traditions of personal honour by violence, becomes arrogant to the point of brutality.
A false notion of personal honour is alone enough to prevent a sympathetic understanding between two peoples.