Let's look at the merit's of the authors argument, stated mostly in the second paragraph. Allegedly contract workers produce low quality or inconsistent work, and that training costs are wasted. All of the supporting evidence is anecdotal, and most of the anecdotes contain heaps of information that is completely irrelevant to the argument. What does the author's bad manager have to do with any of these arguments? Whether Amazon has poor management hiring procedures is another issue altogether.
If a CEO made any decision based on this article alone, he should be fired. At least it may raise enough awareness to get someone looking into it and gathering facts and options for action.