Unscrupulous commercial miners will destroy the public pools to eliminate competition from small players.
That would be counter productive as it would devalue bitcoin and destroy confidence in it.
That assumes that the goal of the commercial farms is to make a profit in bitcoin. That there is no ulterior motive for preserving the status quo commercial banking and money transferring systems, or for bringing their own crypto currency to the market. "See, bitcoin is broken, but here we have this massive farm and will use it to back up and secure bitcoin2."