It's alright to eat things on moderation. What he's doing is moderation, trust me. In fact, one time I had this virus that was eating up some of the tissue in my intestine, and it hurt like crazy. My doctor told me to eat fast food in order to make myself feel better, as un-processed foods made me feel bad. Turns out, she was right. I felt better when I digested!
It's not wrong to eat fast food. It can help you feel better, like what happened with me. Just don't eat it daily.