Illegal narcotics are made in garages and jungles in unregulated conditions BECAUSE they can't be made legally. One of the main reasons they cause so much harm to people is BECAUSE of these poor manufacturing conditions and how they're cut. We should legalize them simply to allow us to create and distribute them in a safer manner that we can regulate and monitor.
Besides, people die many times more from prescription drug abuse than illegal drug abuse.
And alien races likely avoid us because of or proclivity for violence over diplomacy, greed over innovation, and utter lack of common sense. If anything, legalizing narcotics and spending the money treating addicts instead of just tossing them in jail would make it MORE likely that aliens would see us as sensible motherfuckers and contact us.
So... let's legalize drugs so we can meet some hot green Orion women already!