Interesting opinion. In the NatGeo documentary I saw, the semi-legalization of Marijuana has brought an influx of supply, making it harder for (legal) growers to find places to sell to.
If its legalized, it can still generate vasts sums of tax revenue. Look at how much tax money tobacco and alcohol bring in.
I didnt see the show, but I think I am making the point. There will be an influx of legal , non-cartel, growers that will drive down the price. Unlike tobacco and alcohol, the taxation opportunities are limited because you can grow your own. Even so we are probably in agreement, that there is a lot of tax money involved, just not enough to erase past financial sins.
It really depends on the extent to which it is "legalized".
The issue you mentioned regarding taxation applies to both tobacco and alcohol as well - you can grow your own tobacco and make your own alcohol. Many people who smoke marijuana may have no interest in growing their own - the same way many tobacco smokers don't grow their own. Although, the point could be made that marijuana is probably a much easier plant to grow.
Furthermore, legalization does not necessarily allow people to grow for the purpose of selling. For example, it is legal to make alcohol for personal consumption but illegal to sell it.
Even if growing and selling were legalized, the cartels are essentially private in-house, in-industry armies. I expect there'd be a flare-up of violence as they attempt to intimidate legal growers into backing off.
Within a few years, though, they'd probably catch on that they can accomplish the same means via more traditional trusts and regulatory capture. They'll have to, before the market price drops through the floor, killing off their revenues.
Not throwing advocacy one way or another, just an observation on the cartels' likely follow-up response.
The accessibility and drop in price will also surge demand forward. If you can pick it up like a 6 pack or pack of cigs at any convenience store, then sales and consumption should dramatically increase.
If its legalized, it can still generate vasts sums of tax revenue. Look at how much tax money tobacco and alcohol bring in.