Except Microsoft _has_ used patent threats in the past (e.g. against the VirtualDub project, and there are a few more). When the threat comes from Microsoft, and it goes to what is essentially a one-man-show open source project, you don't actually need to get to court.
It's called "a chilling effect".
Furthermore, Ballmer was, and still is, FUDding all the time about Microsoft going to enforce patents that Linux infringes (though not name anything). Even though no action was taken, it also has a chilling effect.
Your defense is acceptable for google. Microsoft deserves to be patent trolled.
The VirtualDub case is an interesting one. I wish the author would have pushed it a bit more. I suspect that there was no threat of a lawsuit, but rather an engineer who saw VirtualDub and was POed. Legal at companies like Intel, IBM, and MS generally won't let someone from the actual product team call another company on a legal matter.
My suspicion is that it was just a rogue employee who frankly probably wouldn't have had support from legal, since legal at these organizations tend to be more strategic than tactical (they don't care about one-off infringers, but are usually pushing a bigger strategic story, where patents infringement is just part of it).
It's called "a chilling effect".
Furthermore, Ballmer was, and still is, FUDding all the time about Microsoft going to enforce patents that Linux infringes (though not name anything). Even though no action was taken, it also has a chilling effect.
Your defense is acceptable for google. Microsoft deserves to be patent trolled.