Before we fall into minority hysteria over Facebook mind control, it's important to note that the control of news has been in upheaval since the rise of the internet. And if social media is bias, its biggest competitor--whoever's flashy headline reaches the top of search engine results--is even more so. The internet has given us the means to insulate our selves from detracting opinions at a level that rivals--or perhaps mirrors--the days of isolated, like-minded communities. It has also given us unprecedented ability to seek out news from a reliable, (reasonably) unbiased source.
If there to be any indignancy about the way that Facebook presents news, it should be directed at those who choose to use it for news, and hopefully take the form of encouraging them to do better.