Google are not actually selling things, merely offering search of retailers (who pay for the priveledge). From the consumers point of you I think this is distinctly different from what Amazon do. On the Google I see they only push Google Shopping through ads and don't appear to alter normal search results. I suppose that they could have an advantage in terms of ads over competitors, but that is the benefit they are selling to retailers so it isn't that different to any other ads. IMHO it actually increases competition by surfacing alternatives to Amazon that would otherwise be the first result.
The competitors that are allegedly being hurt by their preferential treatment here are not selling things either - they are comparison shopping sites.
It is not the consumers this anti-trust action is intended to protect, but those competitors of Google Shopping. The presumption of a lot of anti-trust law is that protecting competition is in the long term public interest that outweigh short term impact on consumers. Some anti-trust actions are motivated by direct consumer interest, but most is motivated by preventing anti-competitive practices by a monopolist from harming competitors.
If competitors of Google Shopping are treated fairly in terms of search results, and can buy the same kind of position that Google Shopping can (I don't think they can), then there would be no issue.
My point in terms of Amazon is not that Amazon search isn't different to Google - clearly they are, though they too have paid third party results on their pages.
My point is that to Google it's their search dominance they need to downplay, not the relatively market position of Google Shopping. Giving their own business preferential treatment is perfectly legal if they're not in a monopoly position. The moment they're found to have a monopoly position, a lot of forms of preferential treatment becomes illegal anti-competitive practices.
They can beat this in two ways: By convincing the EU or EU courts that they do not have a search monopoly, or convincing the EU that they are not giving Google Shopping preferential treatment. The latter I think would be extremely hard given how Google Shopping results are positioned.
The way they can not beat this is by talking about how there's a lot of competition in comparison shopping. If anything, that gives the EU Commission a stronger reason to act on allegations of anti-competitive behaviour, as it means there are Google competitors that may be harmed by any anti-competitive behaviour that might be occurring.
One of the stronger (in terms of product offering) competitors to google were shopping comparison sites. They dominated the search results. Then google pushed an update that pushed them down. However, the manual reviewers really liked them, so in the end, comparison sites resurfaced. Then google changed the manuals, which the reviewers used, so they had no option but to downgrade shopping comparison sites.
So, how is this not malicious altering of normal search results, so you can push out competition?
How about insurance? How about travel? How about google+ imposed on youtube? How about changing ToS of android for OEMs?
