Your argument is seriously flawed. Just because something is made publicly available doesn't mean it's free and clear for anyone to reproduce.
For example, if I don't chain my bike it doesn't mean anyone is allowed to steal it. Taking my bike is still a crime. How I protected it has nothing to do with the criminal act.
Stealing a bike necessarily deprives a person of his property. Copying your competitors when they do something people like is a time-honored tradition and certainly not illegal as long as the copying occurs along certain guidelines. If Bing was scraping Google en masse and just putting a "Bing" interface on it, Google might have something here, but looking at Google's results and deciding they have some better results (and it's unclear if they even did that) and then making sure you have the same "better" results on your page too is not wrong, and deprives no man of his property.
This is merely Google whining that Bing is delivering sort of good results because that threatens Google.
Yeah, as stated I really don't think they'll be able to claim a copyright infringement based on this, one link is not a copyrightable work.
However, it's not that what Bing did is not criminal, it's that it's a non-issue; there is nothing wrong with keeping an eye on competitors directly or indirectly and implementing good ideas or products that you don't have. Everyone does this, it's just normal business.
I don't know why Google cares or is making a big deal out of it, it just seems like whining to me, like they are mad that Bing can just manually compile a list of good results, even if those results come partially from Google. Sorry Google, that's just the nature of the format you're in and the game you're playing. A list of automatically-generated links with no custom or special content, much less a single link, would be a hard case to claim copyright protection, especially since for most actual queries it would be difficult to prove that Bing couldn't have come up with it independently.
I see nothing wrong with it and nothing unfair about it. Do you think the Google guys developed and tweaked their algorithms in a vacuum when they were starting out? You don't think they ever brought up AltaVista or Yahoo! results for comparison and tweaked until they got the same (better) results? I've heard several times that Google constantly has people manually tweaking queries and results, totally extra-algorithmically, to make sure they provide good results for everything possible. So what if Bing does this too? Bing is even being accused of something much less direct. I just see no problem at all, it's just the way this is played.
For example, if I don't chain my bike it doesn't mean anyone is allowed to steal it. Taking my bike is still a crime. How I protected it has nothing to do with the criminal act.