I didn't say that, and I don't believe that, so don't put words in my mouth.
The detainment of the Japanese was unconscionable, and easily the biggest mistep of FDR's career, but he did a LOT of things right for America and the World, and on balance his good FAR outweighed the bad.
FDR's was the strongest supporter of labor that this nation has ever had, and his New Deal was the best Worker-oriented program in history. Because of his support of labor and unions, we got all the workplace protections that we have today:
FDR’s labor reforms, primarily enacted through the New Deal (1933–1938), established federal rights for workers, including the first national minimum wage, a 40-hour workweek, child labor bans, and the right to collective bargaining. Key legislation included the Wagner Act (1935) for unionization and the Fair Labor Standards Act (1938).
Do you think we got things like paid vacations, sick days, and 8 hour work days because the generosity of Corporations? No, we FORCED them to recognize workplace health/safety/environmental regulations, and treat workers like humans instead of animals, or machines, to be exploited to death, and discarded, and FDR was the president that championed all that, and made it happen.
And don't forget, he also established Social Security, so we don't have an Army of old people camping in our streets of every American city.
Then after all that, FDR won WWII, and kept us all from having to learn to speak German and/or Japanese.
So yeah, out of four terms, in which he set American workers on a dignified path for their daily labor, and saved the world from one of the most psychotic nations in the history of the world, he made one bad mistake by succumbing to the fears of the nation during one of our darkest periods. While it should always be acknowledged as a serious mistake, it should never fully define his entire legacy.