Here are some possibilities, depending on the content and tone of the diatribe:
* Digression: A departure from the main topic of discussion.
* Expository passage: A section of writing that explains a topic in detail.
* Satire: Using humor, irony, exaggeration, or ridicule to expose and criticize people's stupidity or vices.
* Stream of consciousness: A literary technique that attempts to represent the flow of thoughts and feelings in a character's mind.
* Soliloquy: A speech delivered by a character alone on stage, revealing their thoughts and feelings.
Please provide the text so I can give you a more specific answer.