I think it's a little short-sighted to only look at diet in terms of carb's, fat and protein. You have to look deeper into each and see what other nutrients it's bringing with it.
None are uniquely bad for you, they just either have the nutrients your body needs, or they don't. So I try to eat more of the stuff that's more nutrient dense per Calorie and ignore the fat, carb or protein proportions of my diet.
For cycling, I do concentrate on consuming mostly carbs during the ride. After the ride I'll continue the carbs and add in some protein for another 20 to 30 minutes before going back to normal stuff.