I was thinking if near the like button they had a report hate speech / fake news button and just didn't show stories much that where that was clicked it would probably make a difference.
Unfortunately, like any kind of downvote system, it would get abused as an "i disagree" button instead.
I was thinking something that didn't notify any users that anyone had pushed it, just made the algorithm share it less and if a lot of people push it maybe submit it to the moderators.
They have a reporting system. It doesn't work (and currently, they don't have any incentive to make it work, because hate speech and fake news are engagement).