Maybe not. Fiery rhetoric is akin to "letting the steam out of your mouth" wouldn't you say? And aren't the ones most guilty of fiery rhetoric often portrayed as blowhards?
post-edit What is the context? I will LIU and get back.
"letting the steam out of your mouth (meaning it does not lead to anything)..."
This seems very clear to me that Avy meant letting off steam or venting. Shall we invent a new word for it? How about geisering.