There's no evidence that tobacco smoke is the least bit harmful when inhaled second hand. That's not true of the effect of psychoactive substances on developing neurological systems. Congratulations on being poorly informed. [But we already knew that.]
That's interesting, because there are apparently plenty of "well informed" scientists who assert exactly the opposite, and, indeed, they spread the word using government-subsidized PSA's, no less.
It would be pretty reasonable to presume that if second hand smoke from cigarettes was not harmful, then second hand smoke, in general, would probably not be harmful. Or does tobacco possess some sort of magical properties which make its second-hand smoke uniquely benign?
In any event, I agree with your conclusion that second-hand smoke from cigarettes is of negligible impact, but, as we have seen, that doesn't stop ostensibly well-informed scientists and other nanny-staters from spreading state-funded propaganda which emotionally claims otherwise.
The debate rages on, and is a prime example of the need for society's do-gooders to rise and save us from ourselves.