Filing patents for defensive purposes

This guy in the article seems to be upset that yahoo is now using the patents they filed for yahoo (promised then, to be only used defensively) in an offensive manner with the intention of doing evil.

Not going into the merits (or lack there of) of Yahoo suing Facebook, what exactly constitutes as a defensive move, when using patents as weapons?

Obviously if someone else is suing you for a patent infringement and you want to ward them off with patents you own (Eg: Google vs Apple) that can be taken as a 'defensive' move.

But if you are on the verge of going down...completely erased from existence, then as a responsibility to the shareholders, should you not use the intellectual property you created (but not yet productized for several reasons - lack of visionary leadership, lack of timing, circumstances etc), as a weapon, legally, to claim revenue/compensation for your technology(created from shareholder's money) being used without your permission? Is that not considered a defensive move? You are fighting for your survival, right? Even if it is not offense the best defense? (Completely playing a devil's advocate here)
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