This show was simply ahead of its time. The official review sees the racial purity/eugenics as a negative thing; did they miss the message of this? Did the writer of this review never take a history, philosophy, ethics etc... class? A variant of George Santayana, "Those who do not read history are doomed to repeat it," must have flew right over his/her head. In my opinion the inclusion of this topic is a positive; because why would it be a negative to expose how many people used to, and some people now think/act regarding ethnic cleansing? The earlier children are exposed to this type of topic the better, at least when it's coming from a ethical point of view, especially when it is from a cartoon superhero (also a role model at this age for kids) is condemning the actions of ethnic cleansing/eugenics.
Anyways, this is a show your children will enjoy and you won't have to worry about graphic violence. It is fast-paced, a very complex message made very simple, that will keep them very entertained.