This strikes me as a valid ethical position, though I happen to think things are more complicated than that.

People who pirate Microsoft products don't really hurt Microsoft, they hurt the rest of the competition.

This, on the other hand, doesn't make sense. You seem to be assuming that the invariant is that the user will not be paying Microsoft. And that might be true for you. If you're not going to be sending any money to MS no matter what, then yes, using MS products helps them somewhat.

For the author of the article, however, the invariant is that he will be using MS products. Since he's going to be using their products in any case, when he is fed up with their policies and decides to pirate instead of purchase until they get fixed, of course this hurts them.

If you want to argue that nothing is invariant, and that the best way to hurt MS is to both stop purchasing and stop using, well, of course that's true, but it's not relevant. What the author is talking about is simply stopping paying for something until it gets fixed; whether he still uses it or not is of very minor importance to MS next to whether or not he pays for it. His goal isn't to destroy MS or make them irrelevant; on the contrary, he just wants a better customer experience.