As a simple example of this, let us imagine for a minute that Amazon and Google go to war. Google drops all search results that point to Amazon products or products in the Amazon marketplace and direct those searches to competitors and competing marketplaces. Google also changes Chrome so that entries into the url bar that are not explicitly for amazon domains do not match or return any amazon domain or product.
Since "Google is not a monopoly" I am sure no one would have a problem with this behavior... :)
That's not a simple example, that's an exceptional poor example. That's like talking about a world with a railroad monopoly and a steel monopoly and discussing what happens if they have a war at their intersection. That's not the point at all.
Google does NOT have a monopoly on searching for the sorts of products you buy on Amazon. In that particular exceptional case, a lot of people do go straight to Amazon for the search.
Since "Google is not a monopoly" I am sure no one would have a problem with this behavior... :)