Before WW I, the German-American community and its civic organizations were opposed to US entry into WW I, with many in active collaboration with German government officials. With the assistance of German Americans, German spies and agents committed many acts of industrial sabotage that were a violation of international law in that the US was a neutral power US at the time.
The German ambassador to the US even warned the US Secretary of State Robert Lansing that if the US entered the war on the side of the Allies, "a million Germans would rise up in revolt." Lansing replied that US would have a million and one lamp posts at the ready.
In such a context, it is easy to understand suspicious and hostile attitudes toward German-Americans. Of course, most German Americans were soon seen to be not only loyal but eager to prove themselves to be patriots and supporters of the American war effort.
“It should be kept in mind that in that era the loyalty of the German-American community was genuinely in doubt and presented a serious internal security problem.”
Undoubtedly. And Japanese Americans were arrested for their efforts to help with the attack on Pearl Harbor. (Spies called in fleet movements so the attack would have maximum effect.)
I mainly posted this so people can use it to make the point you just made when talking about how evil white Americans were to Japanese Americans.
The camps may have been wrong, but it want racism.