Facebook hit by civil rights grievances

It's been a tough week for Facebook when it comes to civil rights allegations against the world's largest social network.
First, the news site ProPublica alleged that Facebook was enabling advertisers to exclude users based on race.
Now Facebook is dealing with an open letter from 73 civil rights organizations to company CEO Mark Zuckerberg who say they are "deeply concerned" about cases where Facebook allegedly censored posts about possible human rights violations -- particularly postings abou