I have zero tolerance with drugs. I had a zero tolerance to them as a single person and the same applies to me as a parent.
If that's due to fear/ignorace on my part, I don't care. I don't like smoking and don't want anyone trying to rationalise that vice to me.
Do I think my dd will try them? It's statistically probable. When we get to that point, I'll start worrying about it then.
Til then, my message is consistent. I've never done drugs and neither has DH. I won't tolerate drug taking in my house. I don't like drugs. When DD asks, or when the subject arises, that's what she'll be told.
In the same way that we don't want our kids to smoke, because it can be antisocial, health threatening, expensive and addictive, I don't want my child to get involved with drugs.
Parachuting, potholing, etc, can be threatening to your health, but are generally not anti-social or addictive, so they can stay on the list. I'm not taking this stance because I'm totally risk averse. I just like to manage my risks wherever I can and this is one risk I can happily live without.