The trajectory of disagreement online. 2009: I disagree. You're a troll. 2019: I don't like you. You're a Russian bot. 2029: Is there anyone out there? Are y

The trajectory of disagreement online. 2009: I disagree. You're a troll. 2019: I don't like you. You're a Russian bot. 2029: Is there anyone out there? Are you human?