If they take the most absurd interpretation or nitpick about irrelevant details that doesn't take away from the crux of the point you're making - and that's the best they can do - are they really intelligent?

Or are you simply dealing with people that "don't have what it takes" to do better?

They simply don't have the faculties to make a better argument or approach from a different angle, it's the best they can do, and the best they can do is just not enough.