Can I get a link or a quote to support that? If that is the case then yes, it crosses a line but I didn't see any in the linked article to support that view.
Edit: I reread the article and I think you are wrong. It specifically says on search pages. From the article
>In 2006, Google started to include "exclusivity clauses" in contracts which stopped publishers from placing ads from Google rivals such as Microsoft and Yahoo on search pages, the Commission said.
>From 2009, Google started replacing the exclusivity clauses with "premium placement" clauses, which meant publishers had to keep the most profitable space on their search results pages for Google's adverts and they had to request a minimum number of Google adverts.
Antitrust law, despite the name, isn't limited to abuses of monopoly power. It includes the use of dominant market positions in one market to reduce competition in another.