Which monopoly does Amazon have that they're abusing to sell hardware?
> Pretty much, you could use the argument you just made against any business that delved into another space.
Nope; only businesses which are a monopoly.
Amazon has no monopoly, therefore the argument cannot be used against them. Plus nobody is stopping Google from opening a new website (e.g. GoogleShopCompare.com) and doing anything they want, using their huge brand and financial power, what they're saying is wrong is embedding it into their existing monopolistic property to give it an unfair advantage (Google.com).
It is exactly comparable to the Microsoft/Windows issues in the 1990s. Microsoft could sell/give away IE, they just couldn't bundle it with their monopoly (Windows) to give it an unfair advantage. Google previously got into trouble for exactly this due to Google Maps being bundled with Google.com.