Lazy J is right- it's digestion, not corn, that produces heat. That's why in the dead of winter I give my horse more hay to keep his gut working and producing heat.
You can't change people minds though, so by calling it a hot feed I hope it helps to limit the amount that is fed to their chickens.
I would prefer to call corn "candy" and fed it to my chickens with that in mind.
Twinkey30- you won't kill your chickens- if you live in a hot climate then fresh fruits and vegies should be cheap. They love apples, watermelon, squash, tomatoes etc. . I expanded my garden to provide my chickens with natural goodies, just treat the scratch as candy and you are the parent doling it out.