Even if it was legal and taxed, no one would buy it, it's simply to easy to make. Legalize all drugs, to answer the question, it's your body do what you want with it.
some people can't think rationally when they're addicted to drugs, not all, but some.
So you say it's okay to see your loved one rotting to death while they're taking crystal meth and it's okay? That they're ruining their life? Some people cannot just get unaddicted, they need help.