Drug users are not bad people. Most drug dealers are not bad people. On my floor in college, the kid who sells drugs is a pretty cool kid: good student, active in sports. There's some social problems he runs across because he's "the kid that sells drugs," but he's a pretty cool guy. He's a typical college student who just happens to sell drugs to the kids who want to buy drugs.
That is not deserving of death. When you talk about killing somebody, you're talking about ending a life, unconditionally terminating a person's future. Some things are worth that (I will hold to my dying day that enjoying the Twilight book series is admitting your lack of will to live), perhaps, but drug selling and drug use? No. Not at all.
As I said: I tried marijuana a handful of times, and I thought it was pretty relaxing. Nobody was harmed. (To go to the extreme, if you use a vaporizer, you're not even risking lung damage, which means that your body seriously is not injured in any way, even minute.) It was voluntary on the part of myself and some friends. We were okay with paying for those drugs; the kid who sold them was fine with trading them for money.
Do I deserve to die because I voluntarily used chemicals? Does the dealer deserve to die because he gave a product to somebody who wanted it? Who is the criminal here?
Enforcing drug rules is basically punishing people not for actually doing anything bad, but for doing something that the government is telling you is a no-no. If I told you that it was bad to, say, whistle, and you whistled, and I told you I'd kill you if you didn't stop, maybe you'd stop, but that doesn't solve the real problem, which is "unalone is a dick who's setting arbitrary, pointless rules". The problem isn't your whistling, it's me.
It's fun thinking of things so black-and-white when you're young, but once you reach the ripe old age of 18, you'll start maturing a little bit.