At the very least, at this point in time, he could have...

At the very least, at this point in time, he could have apologised for being misleading or plain wrong before providing the basis for his argument.
His post was not well written to begin with and he seems to think that correcting himself and being a good sport would project weakness.
e.g.
He initially posted "There is already racism in the constitution, which classified aboriginals as plant and fauna" followed by "A referendum changed that in 1967". The word "is" should be "was" if he believes in his own argument.