Was it well known at the time outside of the US that this was going on? Was there much criticism (or praise?) of the practice from either its allies or enemies? I'd be particularly interested in the reaction in Japan, both in the government and civilians.
This is anecdotal, with no supporting documentation, so it may just get removed but.. I was personal friends with a high ranking member of the OSS who immediately after Japan's surrender interviewed the Japan spy chiefs. When asked for a list of all the Japanese spies in the US, one chief responded "why bother, you put all of them in your camps'. So I can assume that the Japanese position was on of outrage, but for military reasons, not humanitarian.