LU -“Driving and crossing streets are two of the most dangerous things to do, but no one says it’s assur.”
They actually talk about why it’s Mutter to cross the street.
“But- the fact that it is dangerous does not NECESSARILY render it a clear-cut Issur D’oraissa.”
You’re arguing with most Poskim that say if you’re addicted to smoking it’s an Issur D’oraissa!
“but all the bochurim that I know who smoked only did so for a short period of time”
What do you consider is “a short period of time”?