I think a lot of people do take issue with things that call themselves "news" promoting one side of the ideological spectrum.

That being said, social media is just that: something users can post to. Twitter users were not hired to promote a particular point of view, they were invited to share their own point of view. To then go through and cull the people you invited to share based on ideology while still calling yourself a social media platform is where a lot of the complaints (rightfully) come from.