I'm not supporting what Facebook did, but I'm not that bent out of shape about it, either. I already know that what I see in the News Feed is manipulated in some way, meaning that I don't see everything that's posted (and to those who equate Facebook with real life - I think there's an overabundance of 'positive' posts in general that skew our perceptions of others' lives). I think as a user/consumer of mass media, you have to assume that you might not be getting the full picture.
As noted by Jonathan Zittrain and others, companies are running tests all the time to see how consumers respond. This was just handled particularly poorly.