To me, this is no different than how a Grocery store does product placement. In fact, some brands pay a premium to be at the eye level. There are cases where grocery store chains promote their "value" brand above the other competition. This really isn't anything new.
The difference is the monopolistic element. Apple didn't get screwed for bundling Safari with Mac OS because it isn't a monopoly. Microsoft did get screwed for bundling IE because they are. In the same way if you subscribe to the view that Google has a monopoly on search, then it's anti-competitive to use their monopolistic position in search to enter online retail.
They are not entering retail, are they? Targets and Walmarts of the world are still doing retail. It sounds like they are providing an interface and charging specifically for that interface.
Google is peerless and your analogy fails to account for the store not being a disinterested 3rd party. The war between AMZN and Google is bad for consumers because of the precedents it sets as well as the actual market effects. A slightly imperfect analogy that i still think captures the situation:
Google owns and operates a highway and allows gas companies to build filling stations adjacent to the highway. Amazon is only allowed to have their stations off of exit ramps
