I disagree with the statement "what I put in my body is my business" because more often than not, people don't know the effects something has on their body even if they think they know. This is why I'm against legalizing [lifting of all restrictions on] drugs in the broad term, i.e. all drugs by default. If drugs were to be legalized then I suspect there will be an increase in the number of (long-lasting) negative health effects on the populi and a steep increase in the number of accidental drug overdoses of people who want to live. This negative effect will far outweigh the benefit legalizing drugs has on the accessibility of life-ending drugs for suicidal people. In other words, in order to protect the vast majority from making bad decisions that involves drugs and other previously restricted substances, a small group has to suffer the inaccessibility of life-ending drugs.
I don't think preventionists and people with a savior complex have a part in the discussion on whether to legalize (certain) drugs. I think they simply seize the opportunity to (try to) save a person (from themselves) for as long as life-ending drugs remain difficult to access. Their arguments on why life-ending drugs should remain restricted are probably heard, but pale in comparison to what I wrote in the first paragraph.
This is not to say I'm against the accessibility of life-ending drugs. I just don't want it to be an uncontrolled substance. There need to be safe guards.