You are wrong. Australia was a perfect place to live, and the aborigines had lived there since before I can remember in complete harmony with the environment. Unfortunately, immigrants from far away thought that Australia was a better place to live (or to send convicts) than their own country, and fouled it for the Australians. Maybe the aborigines tried to keep them out. Their wooden spears were no match for the dinghys and boats in which they arrived, and they found themselves overwhelmed by people of different religions and opinions. Let us not fall into that same trap, and let's encourage those that we don't want to enjoy as neighbours refrain from emigrating - encourage them to stay in FOREIGN, where Foreign people should stay - make FOREIGN a nicer place to stay, instead of bombing them, and allowing oligarchs to bomb them, and displacing the long-time-previously-oppressed from persecuting them, when there are other continents where the ethnic cleansing has already been done.
Immigration is a foreign policy / aid issue, not a border issue.