First of all, please note that not all of the Japanese-Americans who were interned were citizens. The isseior first-generation Japanese Americans were not allowed to be citizens because no Asians could be naturalized as American citizens. Their children were born in the US and were therefore citizens.
That said, the first word I would use to describe the internment is "unjust." It was unjust because it did not take individual rights into account. Instead, it simply said that all residents of Japanese descent were suspect and were worthy of incarceration. It is unjust to rule that people are guilty only because of their ethnicity.
The second word I would use is "understandable." America was a racist society in those days. In addition, it was a society that was at war and was worried. In such a situation, it is very understandable that Americans would have acted in an unjust way.
The internment of the Japanese-Americans was deplorable, but it was also not surprising in the circumstances.