I'd put it even stronger, especially in this context where we contemplate radically simpler origins of life, that mightn't be "alive" by standard definitions (like viruses), and yet are steps along the way to sufficient complexity to be "alive": that life (in this context) is reproduction.

All at the same time, united in a single goal...

Seeing the wide spectrum of intelligence and education that humans manage it's hard for me to believe we'll ever reach a point of uniformity as a species were something like self-imposed extinction would be plausible.

Not depressed or suicidal, just realising they have no right to gamble with another human being's life.

An honestly held belief that their child would have a miserable, depressed, ill life I could understand - especially because those traits can be heritable. I can also understand sour grapes. However the other arguments seem very ill-motivated.

> An honestly held belief that their child would have a miserable, depressed, ill life I could understand

There's always a risk of that, unless you can 100% guarantee this won't happen you're basically gambling with another person's life. I don't think you have the right to do that.