You were still hurt by it. If you had been taken for study, you would have found that your lungs were absorbing less oxygen per breath than they were supposed to. Luckily for your happiness, your pastime as a kid wasn't swimming or playing sports.
No one saw that your lungs had been disgustingly disfigured, because they were hidden out of sight. What if parents topically applied a substance that visibly did to a kid's skin what the second-hand smoke does to their lungs? Then the kid can argue "it's fine, the damaged skin areas my parents gave me as a kid weren't painful, and I never got sick, and I obviously didn't die".
If parents were to force a kid to swallow a pill that would make their lungs less functional, everyone would call it child abuse. But no one says the same thing about parents smoking around their kids simply because its more "socially acceptable".
There is no need to defend their actions. Your parents should not have done that to you. You did not deserve it. No kid does.
(Steps into time machine, goes back in time, and hands your parents PVs. There...problem solved
)