It is very much hard to answer.
It was mainly because of how the North and the South of America had different lifestyles and economy's. You would be surprised to know that the Democratic party back then supported Slavery and the republicans dint support Slavery.
Plain Answer: Because of Slavery, Way of Life and Different Economy. The Democratic Party would do anything to keep themselves supported.
Answer:
America forcibly removed Japanese Americans following the attack on Pearl Harbor because there was a risk of Japanese spying. America had to ramp up production on almost everything during WWII, and in the event that there were Japanese spies, they could report all our weak and vulnerable points back to Japan. The Internment was, in my opinion, necessary. National security is not something the take lightly. If Japan knew all our vulnerabilities, they could have crippled us. The constitution, if I recall right, doesn't say anything about not being able to relocate a certain mass of people.
Explanation:
