[Elepsis]

Isn't the whole problem with patent trolls that defensive patents don't protect you against them? For better or worse, the current system is largely based around mutually assured destruction. The patent trolls don't make any products, so they don't actually have anything to lose from the assertion of these defensive patents against them.

It seems like what Gruber is actually saying is that the patents Google is violating are legitimate, invented and/or owned by companies that are actively making products based on those patents. The fact that some of those companies (Apple, for instance) may choose to then enforce their intellectual rights doesn't make them patent trolls; having your company's sole business be suing people over violations of patents you purchase makes a company a patent troll.

[tolmasky]

You have the answer in your own comment:

    For better or worse, the current system is largely based around mutually assured destruction.

That is what defensive patents are. Google is saying that they want patents so that no one will attack them (because then they'd sue back, hence bringing on said mutually assured destruction).

    It seems like what Gruber is actually saying is that the patents Google is violating are legitimate

Do you think Gruber has read these patents? Also, it doesn't even matter since they were NORTEL'S patents to begin with, so Apple was violating them too up until the point where they bought them. If these are really valid patents, why wasn't he complaining about poor Nortel's IP being infringed on by Apple when the iPhone came out?