German submarine warfare upset the US because they sank some US shipping at considerable loss of life, rather than because of any inherent moral flaw. Had they steered clear of civilian shipping (trickier than it sounds because some military ships disguised themselves as merchant marine vessels) or at least avoided sinking anything that was likely to belong to the US, things might have turned out very differently.

Moral arguments in political speeches should not be taken at face value, since their inclusion is for emotional arousal rather than reasoned analysis.