Why can't dolphins do intelligent and interesting things without people applying unfounded anthropomorphic qualities to their behavior?
On the same token, who said the anthropomorphic being applied aren't unfounded? There is a lot of evidence out there to support the fact that some animals aren't "dumb" so it's not unreasonable to speculate that some of them might be capable of communicating using mechanisms that we could both anthropomorphise and be complete incapable of understanding.
With regards to the argument that the "Language Log" is trying to make about signature whistles not acting like names, well, they are guilty of assuming that dolphin "grammar" would act the same as human languages. For all intensive purposes they are falling for the anthropomorphic as a result. Or to put in another way "Dolphins aren't following the rules of human grammar, therefore, signature whistles can't be names."