While I'm sure this is a valid reason - that their contractors ripped of the code - is that an excuse to absolve themselves from blame? Heck no! MS needs to held responsible. What incentive do they have to prevent this kind of thing in the future if they aren't forced to take responsibility? This is a big "duh" that this is going to happen when you outsource to a country where the labor is cheap and cheating is culturally acceptable such that nobody gives a darn if they get caught. I've had to work with Indian contractors who ripped off code, which we identified thanks to just a little bit of diligence on our part because we actually want to know what we're releasing and charging our customers for.
Microsoft needs to be held responsible for overseeing what their contractors are doing. That it was their contractors who stole might be reason, but it is ABSOLUTELY NOT AN EXCUSE!