Page quote: "Benatar's antinatalist philosophy: sentient beings are harmed when they are brought into existence, and it is therefore wrong to procreate."
The absolutism and anthropocentrism inherent in that statement renders his whole argument kind of silly. The existence of life itself is inevitably going to cause harm, regardless of how self-aware that particular life form is. It might be smaller degrees of harm, or more indirect, but harm nonetheless.
Sure we should try to minimize the harm we cause others, within reason, on a case-by-case basis, but if your best solution to that is self-imposed specicide, what is the point of ethics?
(Also the comment about natural selection was a half-joke, not a stance on the argument, but your final sentence seems to agree with me anyway.)