Skinny-fying your book is a selfless act. You’re doing it for your reader, who has a lot of books to read. Kicking your book’s ass at the Literary Gym is also a selfless act. 99 times out of a 100, your skinnier book is going to be a better read.
This is particularly true for books that make arguments. If I’m 100 pages into your book, I agree with you, author. Let’s get to the meat, the action of what you’re calling for.