Oh wow, he basically just read from the wikipedia article on "triune brain" in a tone of affected erudition, but forgot to mention the part about "this hypothesis is not espoused by many comparative neuroscientists," and how it's contradicted by actual studies of paleontology and anatomy.
Of course the connection between "reptilian shapeshifters" and "people have a flight or fight response" is the most monumentally stupid part, but what else would you expect from someone using the name "Red Pill Philosophy"?
1. David Icke says reptilian aliens are controlling the world
2. Sometimes our brain stem is called the "reptilian brain"
3. Probably David Icke slightly misread the bones he'd cast and really "the world's operation is dominated by fear and reflexive reactions to stimuli" is what he meant without realizing it.
4. So in short, after smuggling in a lot of premises about what "reptilian brains" are like, and how they're basically free riders in the organism, it's hard to see what relevance David Icke has at all in this story
5. Author excises own brain stem and in vindication of his theory he promptly loses all autonomic functions and is dead in seconds.