That's fair. I would say a person is defined by what they do next.

I think what you're saying is that you should be careful telling someone that they 'are a baby' or 'are dumb', because they might believe you.

I would also be careful of telling someone they are 'acting like a baby' or 'acting dumb', because most people won't appreciate the semantic difference.

In the context of this article, though, I'm not too bothered since the article is about how one can change their baby-like habits. But it is always a good reminder.