I don't like the smoke nazis either. But not lighting up in a car with kids in it makes sense to me - and it makes alot more sense than banning smoking in barrooms.
Ensuring your kids don't eat more than 5 milligrams of sugar per day makes sense to me...making sure your kids eat no more than 12 grams of saturated fat makes sense to me...making sure your kids get at least 5 hours' exercise a week makes sense to me...making sure your kids aren't exposed to harmful radiation, lead-based paint, harsh chemicals, toxic dust, and high-energy electromagnetic sources makes sense to me...not allowing your kids to watch morally or culturally offensive TV shows makes sense to me...teaching your kids manners makes sense to me...
My point is, a lot of things may make sense when it comes to raising kids, but where do you draw the line? And why is tobacco usage singled out as being the most harmful? If it's that bad for you--ban it entirely.