As you might guess, Facebook disagrees with the notion that there were any sinister motivations. It tells Motherboard that its automated spam filter pulled the link "in error." The social network restored the link once it had a chance to investigate, and has since apologized. "We sometimes get things wrong," it says, noting that there are "million of [spam] reports" every week. We've reached out to Facebook ourselves for comment and will let you know if it has more to add.
While the evidence appears to support Facebook's claims, the incident still underscores problems the site has whenever it pulls politically sensitive material. Whether it's a ban (such as the Terror of War photo) or an error (like with the shooting of Philando Castile), any removal is virtually guaranteed to fan accusations of censorship. Facebook has over 1.7 billion users -- it's by far the most popular place to share content online, and even a relatively rare glitch is bound to be noticed by many people. So long as Facebook's automated systems (and increasingly rarely, human overseers) are less than bulletproof, these sorts of incidents are more a matter of "when" than "if."