Foreign ownership (sympathisers including successive Governments call it Foreign Investment) is obviously a threat to our national security not to mention our democratic form of politics:
Just consider the recent Russian invasion of Crymea for example. Russia had invested enormous amounts of money in developing Sevastopol as a Russian Black Sea port over the period of the Cold War. When the Ukraine got its freedom in the early 1990s it automatically inherited Crymea.
Later when the Ukraine expressed interest in joining the EC and by implication becoming a member of NATO, Russia's arc enemy. The rest is history. Russia sent in its army in the form of mercenaries and took the joint over justified by claiming it developed the joint ( had investment skin in it) and that it was neccessary for its national security. Russia now has a similar claim to East Ukraine.
What is to prevent say China from claiming the Pilbara on similar grounds. In fact a month ago a Chinese navy vessel mapped the WA coastline trench ( that's where our subs hide) which extends right up along Indonesia. The Chinese have also built an airport in that region capable of taking airforce jets tec.
The way that the US is heading economically , we simply cant rely on the US protecting us and for that reason we should not be allowing 86% foreign ownership of argueably our best assets so that as such foreign forces may claim justificatuion for military intervention here to protect their assets.
The bottom line is that we cant have it both ways: sell our assets and have control over them
Just try and cancel Rio or BHP's iron ore mining "rights" and you'll see what I mean. You'll soon discover who really owns them!