HBO Go has been out on Android TV for 2 months now and while many other carriers allow you to activate, Comcast still does not . There's no technical reason why they can't do this so the only conclusion to draw is that they are pressuring HBO or Google to pay them to allow activation. That leaves Comcast customers in the dust for a service that is supposedly included with their HBO subscription. I watched them do this same bullshit with Roku, Samsung, and Playstation.
I'm not really sure there's much I can do except throw as much public guilt and shame their way as possible. I've decided that once a week I'm going to poke them on Twitter. Maybe if enough of us do this regularly it will add just enough ugly exposure for them to relent. Feel free to start posting passive aggressive tweets to @comcastcares. Some examples... 1 and 2
You can always stop paying for Comcast TV, and start paying HBO directly. HBO Now is a thing.