Regardless of your gun politics, one web site operated by a self-interested third party is never completely trustworthy as a public forum. I wish more non-tech people would understand this.
[0] http://www.nytimes.com/2014/06/30/technology/facebook-tinker...
People just expect that since they don't see it happen, that it does not.
Imagine that someone wanted to share information which was detrimental to a social media corporation, and he/she published it on that same corporation's social media platform. (This could be an investigative report exposing some unsavory practice, or merely promotion of a competitor's product.) Completely suppressing the story would be counterproductive for the corporation (Streisand Effect), but they would certainly pull various levers to limit the story's exposure on their site, insofar as they expected such intervention to go unnoticed.
This problem is solved by things like federated social networking, where everyone's updates are published by independently controlled sites. You (as a content consumer) would subscribe directly to these sources, and you'd directly control the algorithms that determine which stories float to the top of your news feed, or some user-friendlier version of same.
Facebook already suppresses anything firearm related. They suppress the visibility of gun-related pages (such as how many followers of a hunting page see what was shared on it in their newsfeed) and at the same time bans the paid promotion of posts.
You might not care, or in fact be pleased by this knowledge, but as com2kid pointed out above, what else are they suppressing we don't already know about?