FDR had solid intelligence from two of his main intelligence experts, William (OSS) Donovan and John Franklin Carter, that the Pacific Coast Japanese were essentially quite loyal to the USA. Ironically, Carter's agent (Curtis Munson) said there
were questions about the Hawaiian Japanese. Yet they were not interned. It was one of the worst things ever to happen in the US. It's true impact is actually
minimized by lefty historians, since the main forces behind it were two of their heroes, FDR and Earl Warren.
Interning Arab Americans or Muslims today would be not only be a grevious ethical wrong, it would be an act of matchless idiocy. Indeed its the dampest dream of the middle east Islamists, for the propaganda value alone.
-Eric
The FBI also opposed the "relocation" of Japanese.