Why is it so difficult for people to even discuss antinatalism? Aristotle and many others, well into the 19th century, didn’t accept the idea of a vacuum (the so called Horror vacui in Latin). Nature, according to those thinkers, abhors a vacuum. Probably many of those thinkers themselves, together with a wider public, abhorred the idea of a vacuum.
In a similar manner people seem to be haunted by some horror of non-existence. If antinatalism would reign, they assume, they would never have begun to exist. And, as a matter of fact, they think this would have been bad for THEM.