Speaking of unquestioned prejudices and sloppy thinking - Neanderthals got a bad rap for no actual, researched, verifiable reason. The assumption that they were more "savage" than other early branches of humans is as arbitrary and self-serving (and potentially disproven by contemporary research and re-thinking) as the assumption by white colonizers that black people (or any non-white people) were more "savage" than whites (a massively ironic claim, since the savagery of white colonizers was/is widespread and well documented).

Also, violent behavior is not genetically determined.