Without going into the merits of this particular case, you can get charged for inciting to violence. Indeed that's being arrested for what others could've done. Specifically for what they could have done, but would not have done if you had not incited them to.

For example, if a black man walks into a neighbourhood and someone claims to the neighbours that he is armed and on a killing spree, they are possibly putting that man's life in danger.

Edit: actually a better example is swarming. It's seriously endangering someone's life, so someone doing it can get arrested for what police could have done.