ohh this thread is interesting. I have only just skimmed it and don't know what has been said before.
Anyway, I personally think junk food ( if that's what you call ready made pizzas, nuggets, sausages, beefburgers, ice cream, instant custard etc )can be a useful stepping stone in getting a child to each healthy fruit and vegetables.
My 4 year old is not mega fussy but he has never eaten much of the green stuff by itself. Even turned his nose up at mashed potato. There are a some healthy staples that he likes, cauli cheese, leeks in cheese sauce, the odd chopped up apple, but he can't live on this all the time. Many of his typical suppers contain some 'bad' food to make the 'good' food go down more easily. Say a sliced up sausage with broccoli in pasta, a pizza topped with extra tomatoes, a banana with ice cream, nuggets chopped up with sweetcorn etc.
It's not unusual for me to say, no you can't have more milk (healthy) until you have eaten some of your pancake with banana (healthy) and choclate sauce (bad but tempting). That's because my son will drink mug after mug of milk until he has no appetite. Left to his own devices, he would live on milk and bread and butter. And he has a brother who will eat his meat and two beg, so he isn't copying anyone else.
I don't like food advertising aimed at children but I am not convinced it brainwashes them for life. My youngest son still prefers milk above all else and milk is not advertised. My oldest son, 9 years, did go through a wanting nuggets, seen it on the ads phase, around 3 - 6 years but since then plenty has counteracted this: the odd grown up meal out with us on holiday, the times he is allowed up late to share a grown up supper at home and the cookery programmes he avidly watches on TV (as do lots of his friends) have all served to make him see nuggets and the like as uncool toddler food. Seeing food on TV can have a positive effect. My son might be an exception. He loves 'food glorious food' and will eat lots. But I know he now prefers a supper of braised lamb shanks and french beans rather than beefburgers and chips. Though would try to fit in both