And either way my response is the same:
Think of it this way:
The Player is an actor in a play. While backstage, they see the Bad Guy murder someone. Later on, while ON STAGE, the Player sees the Bad Guy come on stage as well and yells out, "
You, Villain, are a Bad Guy and a murderer! Constable, arrest them!"
Sort of ruins the atmosphere and such for the other actors, the director, and anyone who happens to be in the audience, don't ya think???
Now, as the "Director", I--the DM--yell, "
Stop, stop, stop! What are you doing, Player? Your character in the play doesn't know they are the Bad Guy! Sigh... Ok, everyone, ignore that outburst and back to positions..."
So, if the Player continues to disrupt the play by doing such things, as the Director I will tell them they are fired and look for another Player for the play.