You cannot convince your friend of this. He is already prepared to deflect any arguments you (or Morgan Spurlock) can think of. He will only change his ways if HE wants to--you can't do it for him. It may in fact take an actual health scare of some kind to wake him up.
"We can never save a single human being from a single suffering--that is our despair."
SMILES OF A SUMMER NIGHT
I ask in all honesty/What would life be?/Without a song and a dance, what are we?/So I say "Thank you for the music/For giving it to me."
Actually, there are foods at Wendy's that aren't unhealthy. A baked potato, plain, is about 325 calories less than medium fries. A burger w/o cheese or sauces, is far healthier than one with and chili is low in fat and high in fiber. A diet coke is zero calories. Also, there is grilled chicken. Without added sauces and bacon, it is very good for you. Wendy's in and of itself isn't unhealthy, what you choose to eat there (or anywhere for that matter), is.