Any chemical -- even water -- can kill you. One of the methods of putting an animal down is to inject lidocaine -- the same stuff your doctor or dentist uses for minor procedures -- directly into the heart. It depolarizes the cardiac muscle cells, producing almost instant death. Does the fact that lidocaine could be used for murder mean it should be outlawed?
By the same token, if you huff Lysol (or virtually any aerosol), you can go into brain death fairly quickly. Should Lysol be illegal?
Caffeine is extremely addictive. Taken in not-so-large doses (approximately the equivalent of three or four cups of coffee), it causes heart arrythmia and can result in death. Should it too be illegal?
Responsibility for educated use of chemicals, for whatever reason, rests solely with the user. If people choose not to educate themselves in safe usage procedures -- the data is out there in abundance -- that's on them. It doesn't mean the chemicals should be outlawed.
As I've said before, I am a firm believer in natural selection. If you think hardlining cocaine is a great way to get a cheap thrill, more power to you, but don't expect me to have any sympathy for you when you go into premature heart failure.