Your source did NOT say "often." This illustrates where your "intuitions" about drugs come from---vague statements hazily recalled and colored by your preconceptions.
"By that logic, everything that's dangerous for children should be banned for adults---alcohol, knives, cars, .... "
Why are these things not banned then?
Because your liberal "for the children" argument is bogus.
A majority of the public must not feel strongly that drugs should be legalized
No majority has the ethical authority to tell any adult what he can put in his own body.
Which is it? Ethics or constitution? Feds or states rights? Libertarians bounce all over on these issues.