Nope, their choice. I don't like seeing parents feeding their babies McDonalds fries because it's just a bad start for them but the parents probably think nothing of it. I think there needs to be more education in nutrition as, yes, everyone knows if you eat a lot of Mc Donalds you'll get fat, but I reckon some people don't realise that just because you don't gain weight doesn't mean it's not damaging your insides and clogging up your arteries. People don't realise the impact your diet has on your health. Eating fruits and vegetables lowers your risk of cancers, eating fibre lowers bowel cancer risks, etc.
I eat fast food fairly often (just yesterday I had a popcorn chicken snackbox for lunch mmm) but I am aware that it's high in fast, salt, calories, etc. I know it's terrible for me and so should be a rare treat and not a daily occurrence. Therefore I restrict how much fast food I eat and make sure the rest of my meals are more balanced as well as exercise six times a week.