Your first point ill think more on, and get back to you.
The second point though... How does giving those with few choices already, fewer choices, make them better off?
Also, at what point does it stop? Should everything bad be banned?
No problem.
On the second point- I don't think we'd be giving them fewer choices. I think we'd be rotating out the bad choices for a decent selection.
As for what point does it stop, that has to be handled on a case by case basis- my view is that real world situations and empirical, causal knowledge have to be a part of every such analysis, so I can't give you a specific theory of banning that would map out everything beforehand for that reason. I don't think cigarettes need to be banned, for example, to use something you brought up later on in the thread, but I'm fine with there being a legal minimum age for purchasing/smoking them. A general guideline I tend to use is to consider whether the "choice" in the situation, or the situation itself, isn't significantly burdened by starkly unequal power relations that cause detriment or victimize a particular party. That would apply to the minimum smoking age, for example- we have empirical proof that children whose cognitive capacities are still in development can be unduly influenced by these cigarette ads and start smoking, and I don't consider that a significantly free, well-informed choice. Same reason I don't think sexual relations between a kid and an adult are ok, for example.