https://en.wikipedia.org/wiki/Niihau_incident
It is certainly wrong to say that none might have helped the enemy. At least 3 did directly following the attack on Pearl Harbor.
Internment might have saved 1,000 of lives.
Heck, for all we know internment might have help us win the war. Who's to say what damage a enemy sympathizer might have done. Told about D day? Told about the A bomb? or a thousand other things.
The battle of Niiahu must be brought up in any discussion of Japanese internment. It’s dishonest to debate it otherwise. Still, I don’t think you can find many instances of a free society systematically punishing people by association of their race. When you consider the kind of person FDR was, it makes sense he would do something like that.