That is the opinion of U.S. Presidential Candidate Zoltan Istvan as well as the vast majority in the transhumanist movement. While completely against self-destructive behavior, transhumanists seek complete freedom to enhance their body as they see fit. The goal for them is “becoming the best, most enlightened versions of ourselves,” to quote Zoltan.
Do transhumanists worry that legalizing all drugs will open the doorway for self-destructive behavior? Not really, because we recognize that irregardless of the law, people have and will continue to act out with drugs. Legalizing all drugs will have more pros than cons.
For one, people will be able to address their health problems more effectively. Whether it is trying to obtain marijuana for medicinal use, or secretly battling an opiate addiction, people will benefit from being able to address these issues in the open, without the fear of ending up in prison.
Charlotte Figi is a famous example of a child being treated effectively with cannabis. Ben Swann made an excellent video highlighting the situation with regard to legalization.  Should parents have to weigh the risk of obtaining cannabis illegally or else watch their child suffer seizure after seizure?
When one considers the reasons to legalize drugs, it becomes apparent that they far outweigh the reasons cited to keep drugs illegal, and it leaves transhumanists like Zoltan saying, “I believe it should be crime to not allow mild recreational drugs to people who want them.”
Zoltan raised a great point in a recent article , that future generations may one day look back on us now and feel the way we feel when we look back on the generation that enacted Prohibition. Instead of wasting insane amounts of taxpayer dollars fighting these pointless and crime-gendering drug wars, why not use the money to help rehabilitate people who are addicted to drugs? As Zoltan pointed out, policies such as those enacted in Portugal are working very well.