The only thing you can say to justify FDR's executive order authorizing the internment of American citizens without due process is that FDR may have been suffering a mental breakdown in his 3rd term. It didn't even make sense from a security standpoint. Hawaii was a hotbed of Japanese espionage but the Executive Order only applied to Japanese in California. None of the other states were even impacted. It's possible that FDR supporters were eyeing valuable real estate owned by Japanese Americans or the administration had gone insane. FDR had appointed a former KKK member to the Supreme Court and Justice Black paid him back by writing the majority opinion authorizing American concentration camps.