However, the answer to your question is countries such as Australia have multi-culturalism for at least two reasons:
(1) economic need for labour ("populate or perish")
(2) moral obligation of taking of refugees due to their own foreign policies, such as Vietnam War, support of Israel and Iraq & Afgan War
when you are a nation such as Australia, that is, the product of the British sailing half way around the world to invade a foreign land, you need to populate