I wonder if you’re misremembering. Here’s the exchange:
To paraphrase:
Lucas: Here’s a video someone posted!
FTG: That looks like maybe an AI video.
Lucas: Can AIs make false stories like this? Also, why would someone post a shitty false video?
I think you read the final sentence as, “You’re wrong that it’s an AI video. Why would you post some obviously untrue shit like that?” But I don’t think that’s a clear reading, given Lucas’s calling the video a “false story.”