A coalition of more than 70 groups, which also includes Muslim and Jewish organisations, argues that the website is not clear enough when it takes down content.
Recent cases of Christians discussing homosexuality, atheists and abortion have led to Facebook deleting entire posts and banning users.
In an open letter the coalition calls for the company to spell out exactly why a post has been removed and which rule has been broken.
Facebook founder Mark Zuckerberg said that "sometimes people share content that can be abusive or harmful to the rest of the community".
The group complain that people are being targeted for campaigning whilst "at the same time, harassment and threats directed at activists based on their race, religion, and sexual orientation is thriving on Facebook.
"Many of these activists have reported such harassment and threats by users and pages on Facebook only to be told that they don't violate Facebook's Community Standards."
Facebook has not replied to a request for comment.
