The important part is indeed that Bing is essentially using Google results to boost its own accuracy. It doesn't matter that it comes through a user clicking on the first result of a Google search and opting to send that action to Microsoft
Of course it matters. User feedback is extremely valuable input for a search engine, because knowing what users actually want from a couple search terms is an impossible task for an AI or data mining algorithm. Bing is getting this info from all searches (on their site, Google, portals specific search engines, etc), whereas Google is getting it mostly from their own site. This is the real issue Google is upset about, not the 'copying'.
Google is upset because Bing is doing a much better job of getting this valuable information, and the results are showing. Bing is a real competitor. If Bing were merely 'copying off the test' then Google would be ecstatic... Bing would be forever behind on the treadmill, always with out of date lesser results. But instead Google is worried that Bing will have better results, because what's valuable is not the URLs themselves but the user choices.
If that's not the ultimate admission of "We don't know what the fuck we're doing, and have resorted to copying other people's results", I don't know what is.
First you ignored Bing, now you're laughing at them. ... profit?