If only we could take the Pavlov's dogs approach. Classical conditioning to teach them a lesson! Or, the more common tactic used on cats: spray water bottles. We follow our friends or family member around and every time they do something we deem harmful we spray them with the water bottle. Spray spray spray until they huddle in a corner sopping wet. Then, the next time they decide to perform such activity they remember the water bottle brigade and decide not to make such a stupid decision. Then I don't have to waste the energy I should be using on something important to worry about my dumb-ass friend acting like a kicked off castmate from "The Real World."
So there (with love).