I'm no fan of FB but it's absurd to say their algorithms encourage divisiveness. Their algorithms have no concept of divisiveness, they are simply fitting their cost function which is engagement (well, proxies for engagement). It just so turns out that a lot of people in society want echo chambers where their pre-existing views can be strengthened and validated...that's what is causing divisiveness.

I'm not really sure what FB is supposed to do. Does a fast food company have a responsibility to ensure that people are eating a healthy diet? Where do we draw the line?