Why is the pharmaceutical industry fighting against medical cannabis, when it could be profiting from it instead?

Profit Margins. Ease of growth. Keep it a controlled substance, and they can control access, thus control price. Come out and admit that it can ease the symptoms, and you are left with the public knowing that something they can grow in their back yard with a minimal footprint can ease their ailments, and they will grow it themselves. Now the pharmaceutical companies have lost control. Further pharmaceutical companies are not in the business of curing disease. A cured patient is not a repeat customer. The pharmaceutical companies are in the business of creating customers by treating symptoms rather than curing ailments.There are exceptions to the rule, but they are few and far between. You cannot really ask a corrupt self governing system to police itself and champion the underdog.

THC, the active ingredient in cannabis, has been on the pharmaceutical market for years. Look up trade names like Marinol or for other cannaboids, so the basic premise of your question is already false. The issue is that the legitimate medical usage for these drugs have been rather limited. They have been pretty much only been used for appetite stimulants in folks suffering from conditions that kill appetite. While they do have other properties (analgesia, anti-emetics, etc), there are other drugs that do those functions better. Medical marijuana, IMHO, has been mostly a sham. While some folks do use it legitimately, they could easily get prescriptions for pharmaceutical THC. Medical marijuana has essentially been an abused loophole for recreational use.

Many of the arguments I'm seeing here are about pharmaceutical companies, and about medical uses, and about whether Marijuana is effective, or not. The real argument is why should the government be lording over us all, and telling us what we, as ADULT individuals can, and can't do to our own bodies, in the privacy of our own homes. After that, it is the responsibility of the user, just as is the case with alcohol to bear the consequences or damages of any actions beyond that. If one wants to make the argument that "it's used in medicine" then one can make the same argument for Cocaine, and Heroine (opiates). The argument really, is to ask why so many, are so willing to allow the Federal government to make those decisions for us, and to prosecute a violent, deadly, costly, and destructive drug war as the result of THEIR prohibition on these substances? The medical use arguments are just fringe arguments, but there are valid arguments that medicinal-izing marijuana, or cocaine, or heroine DOES give the government control.... though legalization does so, and just as well, as evidenced by the legal and regulated nature of alcohol products.
Regards all.... Great points, all politely, and cogently argued!