This was the first page I navigated to and I too wondered how the author could make that claim. This is yet another case of someone projecting their personal belief system as objective truth. I'm actually pretty interested in having philosophical debates around the topic of existence, morality, religion, etc. in general, but I'm bored to death of people starting the conversation by assuming their position on the topic as fact without evidence.

For any debate of the sort, certain axioms must be accepted (otherwise, it's impossible to start a debate).

However, that's not the case here, as he does explain why both of these are actually wrong.

It's a work in progress, and the page you got that from is an overview chapter that points to a later chapter that goes into the topics in more detail.