Regarding the tone I concede it is a little over the top, but considering the author works for D-Wave[1] building the future of (Quantum) Computing I think it is not without merit.
It may be better to leave the intro part for the end as it may alienate programmers that have preconceived notions about lisp based on hearsay and not actual experience (i.e. it's enlightening, it's old, full of cruft, hard to read, it's functional, Clojure is the future of lisp).
It is also very much a WIP that the author didn't submit so keep that in mind.
I hope he gets to writing the chapter on Quantum computing: http://learnlispthehardway.org/book/3-14-0-quantum-computing...