I think the guy just grew up. People say dumb stuff when they're young. Not much need for empirical backing when the heuristic (in this case: people mature as they grow older) explains it well enough.
Your narrowly crafted argument is the proper response, but this guy made an empirically testable statement relevant to the sciences. You might not have clicked his profile, but he's also a PhD student of the sciences, meaning he has institutional access.
You won't find adequate empirical backing on personality change over the lifespan, because the ecology of the evidence suggests that personality is stable. Disciplined speech is difficult and worthy.
You won't find adequate empirical backing on personality change over the lifespan, because the ecology of the evidence suggests that personality is stable. Disciplined speech is difficult and worthy.