The political views of a service's customer base should only be relevant to the service when there's an obvious market impetus to encourage satisfying their customers. No one is going to stop using Facebook just because certain right-wing stories get pushed high on a newsfeed, because the users would still have their own community to talk to away from it, and because there's no alternative social website good enough to merit a switch in favor of an agreeable political atmosphere. A hippie vegan restaurant or a gun range, however? Obvious reasons to incorporate bias and not offend your customers, even if it offends non-customers.
An even more glaring example (from what I saw the Facebook thing might have been blown out of proportion anyways (I mean, be honest fellas, Breitbart is not as valid a news source as CNN)) would be Google not giving any negative search terms for Hillary Clinton-related searches, when they would certainly show up on Bing and Yahoo, all the while having no issue giving negative results for Donald Trump. Someone made a YouTube video about it, Google quickly threw out a "Oh it's nothing, we try to hide negative results from anyone", and then immediately changed their algorithm to make it equal with Trump. It's difficult for me to imagine that Google execs were like "Hey, our users lean left, let's bias things towards Clinton to make them happy", all the while Microsoft execs either thought "Hey, our users are exactly split down the middle" or "Hey, let's risk offending our left-leaning userbase".