Yes, both can be true, but why err on the side of the (far) less likely outcome?

In what way can this claim possibly be evaluated? Revealed preference (almost everyone continues to choose living) is the only evidence we have and it's extremely against your assertion.

Even people born into situations that you deem undesirable generally prefer to be alive. Who are you to decide for people that their lives aren't worth living? This seems unbelievably arrogant and entitled.