Having a child is a purely selfish decision, yes, but it's also none of your goddamn business how or why people come to have a child.

For the record, I do wish people would think more about the kind of genes they want to pass on, but at the same time, it's their choice. Dictating others' reproductive choices is a slippery slope. And you act like it's so fucking easy "just adopt!" Adoption is not an easy process, it costs an assload of money, and there's no guarantee you'll get the kid in the end.