Well, that is fair enough, but I wasn't claiming to support Google's position so much as I was pointing out that this is not a case of UA blocking. It seems a lot more innocuous than that.
Rather than tell Google engineers they can't use cutting edge features that they may have even worked on getting standardized, I'd rather go the route of doing what I can to support Mozilla in implementing these features faster. Right now I'm not sure what that is aside monetary donations and code contributions, but either way it seems like a more sustainable future.
If Google were using non-standard features or blocking the entire page based on UA, I'd agree this would be very annoying. But it certainly isn't, as far as I can tell.
On the other hand, Hangouts deserves all of this scorn. It doesn't work in Firefox in any capacity to this day. Very disappointed about that. That being said, it's the only Google service I use right now that doesn't, among Maps, Docs, Search, Drive, Inbox...