There's nothing medical about marijuana.
For those who argue that marijuana is their medicine (for whatever BS disease they claim to have: chronic hangnails, back pain, leg cramps, etc), then I challenge you to answer these questions:
1) Why are you allowed to get this "medicine" in any quantity you want, without any prescription from a doctor?
2) Why are you able to buy this medicine from a 20-year-old stoner with a grow lamp, instead of a licensed pharmacist?
3) What other "medicine" is smoked?
3a) When was the last time anyone took their prescription medication by smoking it out of something that looks like Jerry Garcia's head?
Even many of the folks who carry the "red cards" (MM cards) here in Colorado will openly admit that there's really nothing wrong with them. As a police officer, I've talked to many of the operators of local dispensaries (usually after they get robbed). These guys are down to Earth about the whole thing, and also admit that the overwhelming majority of their "patients" are just looking for a legal way to get high. And, even if local laws legalize marijuana, the substance is still a schedule 1 controlled substance at the federal level, thereby making it illegal (supremacy).
As far as guns are concerned, I'm tired of medical marijuana users claiming that they should be allowed to do anything a regular citizen does, while they are under the influence of marijuana. Simply put, you can't carry a gun while drunk, and you shouldn't be carrying one while high, either. Same goes for operating machinery or motor vehicles, or working in certain occupations.
Personally, the marijuana lobby has nothing more than a weak ancillary association with the topic of guns, and I'd be just as pleased to keep the pot heads out of the gun issue altogether.
That's just my not-so-humble $0.02.
P.S. I'm not even openly fighting against the legalization of marijuana. If the populace of this country wants marijuana to be legal, then so be it. I have NO interest in smoking marijuana myself, but I don't really care if the law allows for it within the comfort of a person's home. But, the current half-legal system of medical marijuana just makes a mockery of the judicial system, and modern medicine, even as it completely ignores federal law.
Additionally, if marijuana is ever legalized, I certainly don't want anyone driving a car or carrying a gun while they are under the influence. Rights are not absolute, and rights have limitations. The US Constitution doesn't grant anyone the inalienable right to get high, nor does it allow for someone to carry a gun when they are under the influence of a drug that can impact their ability to make an intelligent and rational decision.
The slippery slope argument isn't particularly valid in this case anyway. Under current laws in many states a person can already be charged for driving under the influence of many prescription drugs. Just because a medicine is prescribed does not necessarily mean that you are safe to operate a vehicle (or perhaps carry a gun) while you are under the influence of that medication. And, again, marijuana hardly qualifies as medicine.