Apple has created priopritary connectors, closed off systems, paid barriers to entry, and banning apps from their store.
Where is Apple and Microsoft on the scale from Friend to Enemy?
Just that Google is not.
Since things are not black and white, it should be reasonable to differentiate between Apple, Google, and Microsoft.
And in this case I think the point is valid: this policy is bad, both because battery management and notification policy really needs to be part of the core OS in AOSP and not a proprietary add-on and because of the licensing glitch reported here where the client library isn't GPL-compatible.
But that's just one policy. Across the fence of the war mentioned above, it's a GPL-incompatible wasteland where absolutely nothing is possible at all. If you care about free software in the abstract and want to view your war along those lines: Google is behaving badly and needs to be admonished. Apple is clearly The Enemy.
The other things you mention have all been a great service to users, in protecting their security and privacy.
And do not pretend this '1 restriction' is the full extent of Google's user hostility - it is merely the latest straw.
Edit: You may find calling someone an 'enemy' rather extremist - after all, Google is just doing what's best for its bottom line, same as other companies, right? But when they increase their profit not just by providing a good product/service, but also by altering the market/ecosystem/legal system to leave you worse off, what else would you call them? Perhaps sociopath - but "sociopath that's trying to get you for all you're worth" isn't meaningfully distinct from "enemy".
The same with Microsoft. People keep bringing up dragonfly, while conveniently forgetting that bing already works and censors in China.
...and there are plenty of good reasons to explicitly register as a foreground service.
I agree with you that someone's bound to crank out a GPL-compatible lib for interfacing with FCM sooner or later.