>>17945772 (OP)
>Was FDR wrong to detain Japanese people living in America?
Yes, because the order only pertained to the American mainland. The territory with the most Japanese people by percentage was Hawaii, a literal battlefield. The Japanese Americans there were never detained because they were too vital to regular operations at Pearl Harbor.
>What was he supposed to do?
A limited order to merely keep the Japanese at least 20 to 25 miles from the Pacific coast. The decision to exclude them entirely from California, and parts of Arizona, Oregon and Washington caused a great deal of trouble and waste.