The first few messages that humanity received from the Galactics were surprisingly articulate and erudite. However, over time the weird inconsistencies added up enough that humanity gradually realized that they were talking to a Galactic chatbot.
Thus began the Great Crusade against the Galactics.
@simonbp I regret to report that one of the Cosmic Call METI demonstration messages included source code for an ELIZA-like chatbot: https://www.vice.com/en/article/yp985x/meet-the-first-chatbot-sent-into-outer-space