They weren't defending, they were attacking.
Sonos didn't develop anything new or novel in this case - they patented something which arguably should not be patentable, which is the ability to adjust the volumes on all speakers at once.
It's rational for companies to patent everything under the sun as a defensive moat, so they don't get themselves trolled, but this is trolling on their part.
If Sonos sat on this patent, that would be fine, but they're trying to troll other companies, it doesn't matter that it's Google and we hate them, it's dumb.
If Google had copied some core special tech that was the result of Sonos R&D that would be a different story.