I think the expression blood, rain, or horse manure is just a hyperbole used in that specific circumstance to strongly convey the idea that he was going to run the miniseries at any cost.
- an extravagant statement or figure of speech not intended to be taken literally, as “to wait an eternity.”.
Horse manure is used also metaphorically to indicate a nonsensical idea, but it is not related with the meaning used above.
- (euphemistic) if you describe something such as a statement or idea as horse manure, you are emphasizing that you think it is nonsense ⇒ 'Sounds like horse manure to me, Mikey boy,' said Ballpark., It's all a load of old horse manure. (Collins)
Horse manure: The Routledge Dictionary of Modern American Slang and Unconventional English.