1) Cigarettes - I completely agree with. Ban it or don't. Taxing something to oblivion to compensate for the harm being done by it is pure money-making on people's deaths.
2) Aside from the above (because it directly hurts others than the smoker themselves), what you stick in your gob-hole is up to you. Nothing speaks louder than paying a competitor because they have something not offered by others. But people don't. People are choosing to eat this stuff. And despite obesity epidemics, we simultaneously have anorexia epidemics and though - on average - we are getting bigger, that's mostly due to IGNORANCE or APATHY, not whatever is in the food. Anyone who cared would eat other things. Few people do.
4) Margarine's been around for over 150 years. The same 150 years where we've all lived longer than ever before. Note that this is, in general, true of almost all the things that health nuts abhor - salt was a major part of diets going back pre-Roman era. I'm not saying we shouldn't improve (we can't do everything the Romans did because it was "good enough for them"), but it's not the killer you make out unless you seriously abuse it. Or, again, are ignorant or apathetic of it.
3) Celebrity chefs are among the worst: http://www.telegraph.co.uk/new... In preference to all that "artificial" stuff, they suggest you make meals just as bad, if not worse, than the processed foods you abhor.
Kids should learn to cook because kids should learn to cook. Cooking shouldn't consist of sticking a bag in a microwave. However, if you were to suggest that kids learn to cook by using their smartphone to follow a recipe, there's uproar because it's not how you learned to do it.
Newsflash: People no longer eat up a table, in general. People no longer use napkins on their laps, in general. People no longer sit down for several courses, in general. People no longer eat three square meals a day, in general. Because ALL of those thing are bollocks and unnecessary and the legacy of previous generations that invented them.
However, even back in the 60's / 70's you didn't have the sheer range and volume of food available to you. The cuisines and variety of foodstuffs are unbelievable nowadays. The Mediterranean diet is over in the US, the sushi bar is in London, etc.
But the one factor that's the same in all the above - people. People don't care what they eat. So you can either nanny perfectly competent, intelligent, grown adults (your suggestion), or you can let them kill themselves slowly - when they're going to live far longer than you will anyway.
You, and places like the FDA, etc. are on a loser. The second you ban one thing, the manufacturer's will whack up prices until they find another cheap thing they can get away with. And it'll take decades to ban again. And in the meantime, all you've done is made food more expensive.
There has to be controls, of course, but banning something like salt, sugar or fat is really such a dumb-arse suggestion. Put labels on it. Warn about it. Spread bad press about it. Let economic nature take it's course - when I was a kid, there was no Diet Coke, there was no gluten-free food, there was no "low-fat" yoghurt, there was no allergens clearly marked in bold, there was no nutritional information - those all came about through one manufacturer having to compete for a slightly-more-educated customer base than the others. The fact that 90% of that is absolute bollocks and has actually FUELLED thing like nut allergies is neither here nor there.