How many people are doing 300 mile races?? Not very many. My comments about not needing protein are during the normal training that 99.9% of people do and don't involve many rides over 5 hrs. Once you're into very long races like your friend you obviously have to eat some protein while exercising as you're either on the bike or sleeping. That isn't Hammer's target market.

I did look at some of the references from the Hammer paper but they were so old (i.e. 1989) they weren't available on-line.

I wasn't disagreeing that you need to get roughly 15% of your daily calories from protein. I just haven't seen anything that requires it while riding (other than super long races I never do!).