It’s not some big gotcha: it’s unethical because consent is impossible to achieve. You have to have been alive for quite a number of years before you even have the cognition and experience to form an opinion about existing.
But that doesn’t just mean creating new beings is good because it’s impossible to consent. How would that apply to anything else?? By some logic (if you ignore obvious pain signals) animals can’t “tell” us they don’t consent to being butchered and eaten but that doesn’t make eating meat ethical either (I’m not vegan btw.) Having sex with an unconscious person is rape, because they can’t consent.
There may be suicidal animals who want to be eaten and there are certainly people who enjoy non-consensual sex and people who like being alive and believe their existence is a gift. The outcome still doesn’t excuse the act in these cases.
I find this edit even more upsetting. Right wingers love to post the dumbest shit with this emoji as if being arrogantly stupid somehow makes you less wrong.