If that were the case, there wouldn't be a problem. But it isn't. Google requires phone makers to comply with a stringent set of 'compatibility' guidelines in order to license any of their closed-source apps. See http://arstechnica.com/gadgets/2013/10/googles-iron-grip-on-...
Amazon's devices do not have any of Google's services.
However, it's fine... Google isn't doing it for anti-competitive reasons, they're doing it because all of the Google services are needed to have a stable system.
Various custom roms let you install only a subset of the Google services, and that option invariably leads to bugs. Of course Google shouldn't want to support that.
Your complaint is akin to saying that firefox is anti-competitive because to use their XUL interpreter I have to use their mozilla compiler and rendering suite.
There's plenty of freedom already on Android. Plenty of third-party manufacturers bundle their own app stores and users can create and/or install plenty of alternatives.
As it happens, I don't actually believe that Google is being anticompetitive here, I think their actions are pretty reasonable, especially compared to Apple.
But that doesn't mean that every argument that leads to that conclusion must be valid! The statement I was replying to was not. Amazon devices prove the point: as they don't comply with Google's requirements, they are unable to ship any of the Google's proprietary services even as part of the process antsar was suggesting in the GP comment ("part of the setup process [could be] to select an app store" [from a selection including the play store]).
