Alternate theory: this is samsung throwing their weight around. Google purchased Moto because they wanted to get into the devices business, Samsung tells google to get rid of it or else they will continue to diverge their ~70% of the android market away from google's version of android.

Google clearly wants to be a hardware manufacturer: they've been circling the market for a while now, trying different things: they bought moto, they bought nest, they keep doing nexus devices, glass, the ever-growing lineup of google play editions, chromebooks... I don't think they bought moto just to be a bully, or just for the patents.