Maybe we're simply not intelligent enough to realize that our own form of communication is actually very primitive, and a sign of little intelligence, not great intelligence.
The claim he made is that people think intelligence requires linguistics - he then goes on to say that aliens may be communicating in some different way that doesn't require linguistics.
At any rate, a number of the arguments made in this thread are absolutely absurd. Of course intelligence doesn't require linguistics - linguistics is merely one of the markers of intelligence.
And of course creatures can communicate without language - it happens in nature every day.