An intelligent, wealthy, employable person can dabble with them, have a good time, and usually get away with it. Should they get addicted and screw up their lives, they can usually get help and bounce back without permanent consequences.
People who're a little less well-off intellectually and economically aren't so resilient. Should they get addicted to hard drugs and screw up their lives, they usually don't bounce back from it - their lives are ruined forever.
Since HN is full of intelligent, wealthy, employable people, the comments on this thread don't surprise me a bit. And yes, I agree that drug policy in the United States could stand to be reformed a little. But when evaluating the harm a person's actions can cause to society, I wish people would think a little more about not just themselves, but that vast chunk of society that's not lucky enough to not be as privileged as we are.
Aside from that - let's posit that Ross Ulbricht's arrest and punishment and the shutdown of The Silk Road doesn't impact consumption and the consequent negative effects at all. I've still got no real moral qualms about punishing someone who enriches themselves off so much harm to others. Yes, there are many people in this world who do equivalent harm that we don't punish, and that's unfortunate, but that doesn't change the rightness of Ross's punishment one bit.