My (sarcastic) theory is that the name was chosen out of a very specific hatred of the Karen people of Myanmar and environs. They may be a third world tribal people, perhaps even indigenous, but since they aren't African, American or Australian they don't count in the minds of the average western wannabee world saver. Insulting them by using their name as a slur is perfectly OK, unlike the horror of insulting some random person one doesn't know by calling that person "them" rather than checking their pronoun preference.