The outrage against AOC should be directed at her adding "never again", not at her using the words "concentration camps".
It is actually historically illiterate to regard "concentration camp" as equivalent to "death camp" or "extermination camp". The original concentration camps (to which the name was first applied) were outdoor prisons used by the British to deal with the Boers during the Boer Wars and were not intended for the purpose of mass murder, but only to control the Boers by concentrating them in prison-like conditions, just as the detention centers are intended to control illegal immigrants by concentrating them in prison-like conditions. She is also correct in applying the phrase to the detention camps for Japanese-Americans during WWII: they also followed the original British model without adding mass murder as the Nazis.