If all people were intended to be of 'the same race' and 'one race'... why does this sign exist?



Can anyone explain why even liberal Astrologers know Cancer is the sign of racial matters, ethnic defensiveness and one's origin, also that the Moon and the 4th House deals with this, yet somehow also think all distinct races need to be exterminated and amalgamated into some blob of vague 'humanity'?

Furthermore, if other things ruled by Cancer such as women, the public and one's house need to be guarded and protected, why is race irrelevant?