Many of them were very vocally anti/US, as well, though no one wants to talk about that.
After Pearl Harbor the US military was terrified of an attack on the US west coast, which was ridiculously and totally undefended. Fully 80% of American aircraft manufacturing was on the west coast and well within gun boat range of the coast.
Scared hardly describes the feelings of the military!!
Gen. Stillwell was sent there to assess and set up defenses. Said he never slept because of the nightmares he was having. Thousands of unvetted Japanese Americans at large made things worse!
And we knew, from decoding intercepted Japanese naval and diplomatic radio communication, that the Japanese government was attempting to operate espionage and sabotage operations on the west coast.