There has been a recent wave of racist posts about Baltimore, including one linking to an ugly article and saying, in the post, that it is "open season on [highly offensive term for African-Americans]". Maybe Google has a team to manually review these threats and call the police, but, in the mean time, Google+ algorithms have been putting these posts on my feed repeatedly because they are "Hot on Google+" I thought I might have to leave this social network.
Turns out that you can disable "What's Hot" on your timeline entirely. I've attached a cropped screen capture. Full instructions are at https://support.google.com/plus/answer/1686118