What does age have to do with responsibility and maturity anyways? I know a teen mom who got a kid at the age of 18 (got pregnant at 17). Wonderful mom, wonderful kid. She had another one by choice. Same father, who has a solid job. They have a house, a good life, etc. I also know a guy who got his third child when he was over 30. He was sulking and making snippy comments because it wasn't a girl, accused his (third) wife of cheat, starting cheating on her himself, divorced and doesn't want to see his latest child anymore.
(ps: yes I know that several marriages aren't always a sign of immaturity, but in his case it very much was)
Hey, I even know a couple of 19 (both) who already had a job and decided to marry and have a kid. They were just ready for it.
The comment of that man just piled assumption on assumption: the mom being a teenage, the mom being immature, the mom having an accidental baby, thats three!