Problem is, they're right.
Recalling another thread or two that I read (I can't recall which ones for the life of me -- Sorry!), it might be that their network has the capability to be the fastest. In a perfect world, their infrastructure at a certain point would allow them to be the fastest of the listed networks. Problem is, we don't live in a perfect world. Far from it, as we see with the real average speed listed for AT&T. So while they are unlikely to be in any legal trouble over false advertising, it's still unethical to claim they're the fastest, and Luke Wilson is still a douchebag.