Roosevelt justified the order on the grounds of military necessity, declaring that Japanese Americans were a threat to national security. Anti-Japanese sentiments had been developing in the U.S. long before WWII had even begun.
Roosevelt's infamous solution to this problem was Executive Order #9066, which authorized the internment of between 110,000 and 120,000 Japanese Americans on the pacific coast. Roosevelt justified this authorization on a legal argument that the need to protect the country from espionage outweighed the individual rights of those that were interned.
It is true that semantics (a branch of language dealing with the meaning of words) considers both the connotation (the feelings a word evokes in you) and the denotation (the actual meaning of the word) of words.
