You could also easily just slap liability to the seller of known harmful substances (see the sibling to your comment) or enforce warning labels as on tobacco products (eg "this product makes you shoot people and shooting people will get your thrown in jail").
Wouldn't it be good to prevent the shootings before they happen?
But this thread is about how the cure is often worse than the disease with prohibition. See: 18th Amendment, War on Drugs. Concocting a hypothetical scenario where the drug is Disney-villian evil and enforcement is not an unmitigated disaster is hardly a decisive rhetorical victory, wouldn't you say?
It _is_ a decisive rhetorical victory, even if you don't like it.
1) The scenario proposed seems...outlandish. I could argue for a host of provisions in law or the Constitution based on the possibility of widespread development of bulletproof skin, but I fail to see the utility of doing so.
2) Even within the hypothetical, it is possible (I would argue probable) that banning the evil rage drug would simply make the situation worse than alternative solutions, in which case the proposed amendment would be a positive.
Edit: You could argue that the above amendment is also ridiculously unlikely to pass and isn't worth debating either. You'd probably be right.
2) No I don't think we would need to ban it. Allow people who want to use it to lock themselves in a cell for 12 hours and rage against some padded walls. There probably would be a thriving market for that sort of thing [0]. We let people drink and if you drink and drive someone will probably die - the solution is not to let people drive after drinking. You're basically describing a strong form of alcohol. We already tolerate this sort of risk.
If you want to argue that a substance exists that is so terrible that people who consume it need to be locked up, you should name the substance and provide some argument for why it is so bad. The present state is locking people up for no obvious reason.