A new argument for antinatalism Trying to tell everyone that they should not procreate due to an alleged pre-eminence of harms is a pessimistic imposition. It's just that it's intellectual rather than physical. Natalism bestows benefits that antinatalism never can (except for perhaps helping some people who already exist).
Trying to create too many people can cause damage in the long run. This doesn't mean one should not do it at all whilst keeping practical considerations into account.
Any rational person who honestly analyses the complexity of the sentient experience should realise, I think, that saying that it's never acceptable to care about the value of the positives as long as there are any harms is as ill-advised as it gets.
People frequently decide for others in order to give them a good they deserve, such as saving someone even if there's a small chance that they might not like it. We don't see this as a problem because we recognise that the aforementioned case, whilst unfortunate, should not make us forget about the majority of cases in which people would appreciate being able to have a good they couldn't have asked for. If someone says that this isn't analogous to procreation because nobody needs to be saved, then one could also point out that neither can an act that doesn't violate existing interests be considered an "imposition". Universal antinatalism, in what some could call insidious paternalism, prevents the bestowal of positives that innocent sentient beings deserve (and if it's good to not impose even if nobody benefits from it, then there isn't a good reason to think that it's not bad to not create a positives irrespective of whether or not inexistent beings need it) and could mislead innocent people into thinking that they should avoid procreation because it's an ethical obligation, even if they become miserable due to this. It hasn't been shown that the prevention of the positives is acceptable in objective terms.
It is extremely saddening that people do have to go through severe harms and be forced to endure an existence they cannot find any value in. I hope that ideas such as transhumanism and the right to a graceful exit can help reduce both of these harms significantly. But, having said that, it simply doesn't make sense to ignore one side of reality altogether. It's incredibly myopic to essentially say that all the happy people that exist essentially didn't deserve to exist due to mere presence of the negatives. And if not creating someone respects their autonomy, it also diminishes it to a greater degree by not giving a good that cannot be solicited prior to one's existence. One's subjective perspective that conveniently misses the value of optimism and the presence of the negativity bias cannot be considered a valid justification for preventing all happiness. "Oh, you enjoy life despite suffering (perhaps more than me)? That's irrelevant, since you should not be here due to the fact that creation also entails some risks," is hardly a pleasant sentiment.
Unforeseeable benefits also matter. The person might think that a the individual would just get through life, but it's quite possible that they would have inestimably valuable experiences that would stem from their unique perspective, such as the joy that can come from the pursuit of knowledge and the happiness that is experienced by those who really care about meaningful relationships. This "known unknown" isn't as infrequent as some might think.