a verbal attack
diatribe - rant
A ‘diatribe’ is a forceful and bitter verbal attack or criticism against somebody or something, usually in the form of a speech or rant. It is typically delivered in an angry, unhinged way, which means that it tends to be ignored or not given credence by the person(s) forced to listen to it.
I just asked her if she had seen the new gadget and she launched into a diatribe about consumerism.
The politician did not so much give a speech as deliver an hour long diatribe about the current state of the country.
His emails did not offer any constructive criticisms. They were just lengthy diatribes which I promptly deleted.