Even if the drug proved to be safe, the government would stop pushing the "if you take this you will die angle" and they would start promoting how it would make you steal, or be irresponsible, or non functional. That's the problem with propaganda, it isn't accurate.
I think that all substances should be legalized regardless of neurotoxicity, or other harm that it may cause. It's proven (by all people who use illicit drugs) that prohibition does not work. The only thing that prohibition ensures that is criminals make lots of money. I think that consenting adults should be able to make the choice for themselves regarding what substances that they ingest. I also wouldn't mind if the government placed a tax on all recreational substances, I would gladly pay the "peace of mind" tax to know that the substance I was picking up was 100% pure and non adulterated.
The government has a long way to go, if they in fact ever make the consideration to being legalizing substances. And as a previous poster has said, it will be extremely difficult to do any research showing long term effects and the potential of neurotoxicity since the substances are illegal.