I think he was asking about real-world reproductive activity, rather than a notional 'fitness'.
My interpretation, is that he thinks he spots a flaw in Darwin's theory: If survival of the fittest is true, then (according to his views) why are do many unfit people reproduce so much?
I answered by pointing out that it is
reproductive fitness that ultimately matters. And, a lot of factors go into that, not just the subjective notions of 'fitness' we humans often notice.
To add to that:
The rich and healthy have adapted a survival strategy, where they don't need to reproduce as much, because their children are more likely going to be healthy and survive.
The sick and poor have adapted a strategy where they just try to have as many children as possible, in hopes that some of them will survive.
That summary also over-simplies the matter. There are a lot of complicated other aspects involved. But, my point is:
Darwin's theory helps us develop explanations for the observations in the opening post. The observations are not really flaws, at all.
By caring for our sick and elderly, and through manipulating our environment, one could argue that humans have co-opted natural selection.
We humans have the ability to change the course of our own fitness landscape, more so (it seems) than any other life forms.