Exodus 20:16. "Thou shalt not bear false witness against thy neighbour." This is the Ninth of the Biblical Ten Commandments: Right up there with murder, theft, adultery and idolatry.
Yet every day on Facebook, I see posts, from people who claim to reverence the Ten Commandments, that copy false accusations and slanders. There is the photoshopped picture that pretends to show Hillary Clinton shaking hands with Osama bin Laden. There is the photo claiming to show Michelle Obama txting during the pledge of allegiance (it's actually some reporter). There are fake quotes that pretend people said things they never said. There is the incomprehensible rant falsely claiming "Snopes got snoped." There are more every day, mindlessly copied and shared without checking by many people, simply because they attack people they dislike. This is false witness. It is spreading malicious lies to slander someone.
In John 8:44 Jesus says that the devil is the father of lies. The word "devil" is an English form of the Greek word "diabolos" which actually means slanderer, false accuser. So, when you post a false accusation, you are quite literally the devil.
By contrast, Jesus said: "I am the way, the TRUTH, and the life," so if you want to follow Jesus, you must follow truth. If you follow lies, you are not following Jesus.
But, you say, you didn't realize it was false! Is ignorance a defence? No, it is not. If you spread accusations that you don't really know to be true, it is still bearing false witness. But anyway do you really want to claim ignorance? If you don't know what you are talking about, why are you posting? Why post in ignorance? All you do is prove your ignorance.
Spreading malice in ignorance is gossip. The Bible condemns gossip in the strongest terms. Romans 1:29 says this about the Godless: "so God gave them over to a depraved mind, so that they do what ought not to be done. They have become filled with every kind of wickedness, evil, greed and depravity. They are full of envy, murder, strife, deceit and malice. They are gossips, slanderers, God-haters, insolent, arrogant and boastful; they invent ways of doing evil."
See who gossips are grouped with?
There is simply no way to reconcile careless posting of accusations with Christian ideals. It is anti-Christian. If you are going to make accusatory posts, you have a Christian obligation to at least make sure they are true. If you can't take time to check before you post, don't post. And if you check, make sure you check reliable sources, not just the same scurrilous partisan echo chamber sites that pump out the lies. If you don't know how to check it, or just don't want to bother checking, just don't post it. It's sinful.