Here is the problem as it has been stated before, you only gave people two options:
No. It is not performance enhancing. It's just a plant
Yes, if they smoke it means they are incapable of making good decisions
So if someone says yes, it's cool to be a pothead or whatever, and it's no big deal, but if they say no it's the end of the world and that person is an idiot. You basically make it seem like yes it's cool and if someone says no they are evil
Personally, I will never touch the stuff, never had a desire to, but i don't crucify anyone who does, it's your business , it's your body. The problem is that you spout #'s that you may not have proof of, (40-50%) of med students do it? Prove it. I don't care what they do in their free time, but the minute those actions impact another person's life, then you have a bigger problem.