I really love the people who claim that second hand smoke is worse for you than first hand smoke.
I am not really sure how you would interpret the GP to "second hand smoke is worse for you than first hand smoke." I do not really see it from the post. What I am seeing is that how second hand smoke would affect the baby of a mother who is in her pregnancy and not a smoker. The question is related to the GP's parent post talking about a mother who is a smoker but stops smoking in her pregnancy.
Also to me, there is no level of danger between first and second hand smoker, but there is only harmful or not harmful. To me, both types are harmful. The different between first and second hand smoker is the first hand smoker does it at will but the second hand smoker is being forced to take it. In other words, first hand smokers do smoke because they want to (usually wherever they want if no restriction); whereas, second hand smokers are there for a reason that is not for breathing in the smoke. If one wants to argue about these people, who do not smoke, should not be there, that is a different topic and should be discussed else where.
*I was a non-smoker who roomed for a couple of years at college with a pack a day smoker. When I moved out I found I'd become addicted and started smoking (stupid, I know).
I was growing up with a father who smokes a pack a day, and none of us (7 children) is a smoker (ever). Yes, we all are second hand smokers for many years (longer than a couple years you claimed), so being a second hand smoker has nothing to do with becoming a smoker.