The problem isn't 'herp derp how do we make monies from weed', it's keeping a vast government-prison industrial complex well funded. Imagine how many fewer prisons (with their guards, fewer federal agents, and various law enforcement jobs will be lost with legalization
That's pretty much point 2 in my post. It's not just making the same amount of money via the tax, it's getting the money to places that need it to keep operating.
If you legalized it/taxed it, I'd assume the tax would work similarly to other "sintax" items, the overwhelming majority of which are not taxed at the local level (think gas and alocohol tax). Conversely, a huge chunk of the money being made right now on the business that is the criminalization of marijuana is being made at the local level (think criminal fines, court costs, etc.).
The money would still be there - maybe even moreso - it would just be taken in though by a different taxing authority. You think parish Sheriff's offices are going to want to cut budgets/personnel when the potheads can no longer be fined and imprisoned? No way. In Louisiana, Sheriff's are like little kings. They wield an incredible amount of power.
All government policy chiefs understand that pot could be taxed, and the money raised would exceed the amounts raised via criminalization. That's a no brainer. It's how to get that money to places getting it now.
No one's balsy enough to get in front of the people and say something along the lines of "look, we know this stuff isn't that bad, but we can't afford to operate without the funds it generates. so we'll be all for legalizing it if you can tell us how to get our hands on the tax money part of the deal".