"Poor people have kids all the time, a lot of times they are even smart!" is extraordinarily classist. It makes a joke that based on the assumption that the majority of the time poor people are stupid.
Not a good look to say something like that.
I think there is a charitable interpretation of that sentence where they were being tongue-in-cheek with the understanding that readers would all agree that obviously being born to a poor family does not determine your intelligence.
The rest of the post seemed to indicate they didn't deserve the benefit of the doubt there.