They know it has hallucinogenic effects, but they refuse to accept that it's having a negative affect on the cognitive capabilities, and that's just ridiculous. If you're ingesting chemicals that are altering your brain's chemistry, it stands to reason that it's going to have unintended consequences down the road. It's no different than the people who know they're literally drawing smoke into their lungs, but can't imagine that it'll affect their lungs' ability to function down the road.