Ask him if he ever did the pineapple/jello experiment. Remember that one anybody? Take canned pineapple and mix it into the jello and it sets up nice and rubbery. Do the same thing with fresh pineapple and the jello stays liquid. Canning kills everything live because the product is heated, just like pasteurization, so the enzymes in the canned pineapple are killed and can't break down the protein in the gelatin. So in the same way all the valuable constituents of honey would be killed if heated too much.
It's about all those great enzymes, nutrients, anti-oxidizing compounds and many others that get zapped if you cook your food. I eat the majority of my food raw and do a lot of fresh veggie juices, and the difference in my health and energy has been huge in the last few years. Just tell him to look up Jack Lalane if he has any questions!