Why did United States citizens feel that Japanese Internment camps were justified during WW2?

Japanese Internment camps were justified during WW2:

Under the presidency of Franklin d Roosevelt, he felt that japan espionage is operational in America and he ordered all the Japanese Americans to be as interns who are confined in concentration camps. They were given a lengthy inquiry form which urged the Japanese Americans to prove their allegiance to America and it asked whether the Japanese are willing to serve in American army.

Those who negated were brutally punished and those who affirmed were let free. After the Nazi Holocaust, these types of concentration camps were started by US too which is almost considered unfair.