If he used "the point" instead of "there is a point" then a need to add a "colon" or "is to" and some changes involving the object of the sentence to help correct the alteration you made with "the point".
Quote:
There is a point of having a large vocabulary in a language - its helping people say exactly what they mean.
The point of having a large vocabulary in a language is to help people say exactly what they mean.
The point of having a large vocabulary in a language: to help people say exactly what they mean.
) because I don't thing my knowledge of grammar is enough to sustain my argument. 
