Even if it's just 5-10% (difficult to prove one way or the other, but some have estimated it's within this range) that's a massive amount of people on a global scale. That's enough to influence elections, for example. Scrutiny seems reasonable.
Not sure what you're getting at about elections, are you saying that's a reason to intervene? I don't really want the government making policy for the purpose of influencing election outcomes.
100% of people will need to give up some luxuries so that everyone can benefit, and especially <<vulnerable groups>> can benefit.
Taxes work the same way. Laws in general work the same way (otherwise we'd assume everyone is smart, fair and calculated heck, perfect, all the time).
The only thing I can really get behind is stricter controls on individual ingredients that are very clearly unhealthy and obviously don't need to be part of your diet (BPAs, trans fats, etc). Once you start messing with society's macros though it's fraught territory and very easy to do harm IMO.