The only reason that ultimately matters is that poking smot is not wrong, and putting innocent people in jail is. All that other stuff is incidental.
If it helps the cause, then use it, but I think most of it just confuses the issue, and opens it up to more fallacious counter-arguments. If we argue that certain unethical things should be stopped because they are impractical, then what do we say about the ones that are practical?
You want reasons it might be practical to imprison innocent people? Homelessness, insanity, youth, unpopular opinions, unpopular religion, guilty friends or relatives, wrong place at the wrong time, looking suspicious, bad taste, ugly, body odor, to name a few.
Marijuana proceeds fuel the expansion of criminal orgs that also practice human trafficking and import harder drugs. Legalization will destroy many of these organizations.
will it really destroy them? it seems like they will be able to provide the same product for a much cheaper price because it will not be taxed.
i don't know much about this proposition, but would it still be considered illegal to be in possession of marijuana not sold/taxed by authorized dealers? would anyone really be able to tell whether a person is in possession of marijuana that came from an authorized dealer or from a gang member?
A commonly cited estimate is that fully half of the income of the Mexican drug cartels comes from marijuana. If you deprive them of that revenue they won't go away, but their influence will surely be substantially weakened.
Imagine if marijuana were farmed using truly modern big-agricultural techniques. The price would be significantly lower, so even if you added on a nice profit for the company and a tax it would likely still be cheaper and significantly higher quality than black market product.