Some decades ago they also said cigarettes were not dangerous. Purifying radium was not dangerous, either. Then, decades later people started dying of cancer. They say cell phones are not dangerous, though a friend of mine who did a PhD in computational bioelectromagnetics is not so sure.

I am concerned about the ethical aspect of it. If I were a scientist who had spent 30 years researching the effects of marijuana, I would say that: "scientific evidence seems to suggest that marijuana is not dangerous, but people should take into account that future research could lead to different conclusions". People should decide, and have already decided. There's a huge market out there and it's a scandal that marijuana has not been legalized yet.

Unless you are absolutely sure there's no danger whatsoever, you have no right to say that any fear is a joke. Your certainty stems from your ignorance, and this is not supposed to be offending. I think pot should have been legalized decades ago, and we're not moving fast... we're moving slow. Legalize it ASAP. Period. But do not advertise that there are no dangers, because you don't know. Moreover, the way you consume pot might be the danger, not the pot itself. I mean the paper used to roll the joint for instant. The hot air is known to increase the chances of throat cancer. Lip cancer is a problem. Using a water pipe should be safer. I know I know nothing, but for a layman you seem awfully certain.