I happen to be involved in certain areas of law enforcement (so yes, I do know a few things about substances of abuse and the users themselves.. as well as "technology" as you stated); I've heard your arguments over and over and over again. Unfortunately, it didn't hold any weight when they first started using it as their argument, it doesn't now.
The levels of dopamine released from the caffeine in a cup of coffee are considerably less than the levels released from a single joint (and obviously, this is one of the more inefficient delivery methods) Caffeine doesn't constrict the blood vessels in the brain, causing over time, permanent loss of capacity (again, much like alcohol's long term negative effects on the brain).
There have been literally hundreds of studies on THC and decreased brain function. How many successful Doctors and scientists have you ever heard say "I'm a habitual marijuana user"?
One of the best arguments is the one that goes along the lines of this "weed is natural; nature doesn't hurt you"... This is a ridiculous argument on two levels; one, if nature is okay for you... there would be no such thing as poison plants that will kill you if you eat them. And number two, Marijuana as we know it today is far from natural; it's been bred and genetically manipulated/modified. It's nearly impossible to find marijuana as nature intended it today, and if you did... you would be entirely not impressed. It goes right along the same lines as the tobacco industry increasing the tar contents of their products; you're putting out a product that has a greater effect which will make your customer more happy (while totally disregarding their health), and as a bonus, you're increasing the physiological as well as psychological dependence.
Trying to tell me that because I'm not a user that I can't make a judgement... that's laughable. If this theory were true, I should have to sleep with a man to know I'm not gay. Well guess what, I've never done any such thing and... I know I'm not gay. But interestingly enough, you make an argument that marijuana/THC isn't a gateway drug; yet you yourself said you've experimented with other drugs. Wouldn't your argument of exclusion do to applicability nullify your views? Then you compare it to Felonious auto theft; this is truly laughable! I hope you were high when you wrote this because it really is a bad comparison. You're telling me that if you steal a car, the only reason you would progress onto robbing a bank, rape or murder is because your initial act was illegal? This argument is like saying well "yes, it's a gateway... but only because it's illegal to begin with". If that were the case, we'd have a great deal more serial killers to contend with. There are a select few who commit crimes just because of the adrenaline release it provides. Most do it for one of two reasons; necessity (weather actual, perceived, situational or self-inflicted), and simple psychiatric "dysfunctions" (I put it in quotations because there is a difference between this and clinically "insane"; one is simply the lack of aversion to crime and the general lack of ethics, the other is an actual condition that inhibits control and the differentiating between right and wrong). Anyhow, I guess if we legalize auto theft, we'd eliminate all crime... You should run for public office on this initiative!
And since you brought it up... Legalizing marijuana wouldn't decrease the likely hood of users moving on to "bigger and better" things. Nearly half of all habitual alcohol users have also used marijuana within the last year (this statistic is from 2006 and it's actually around 44%, but that's close enough to half for me), over half who use tobacco and alcohol... but, for those that don't use alcohol or tobacco, it's less then 15%. What does that tell you? Yup, it tells you that legalizing on particular drug doesn't all of a sudden make people content with the stimulation they have at hand. The fact is that persons who consume or use any kind of recreational drug, legal or not are more likely to progress up the ladder, and the further up the ladder you go, the more likely they are to continue climbing (it was somewhere around 60-65% of marijuana users had tried other illicit substances). So, you draw the line somewhere, in an effort to maintain a higher level of society (if you can name anywhere that ALL drugs are legal and it's perfectly safe to walk down a dimly light street at night... I'll give you the win... drug use as a whole degrade society). Why marijuana and not tobacco or alcohol or even caffeine? Well, tobacco is on its way out; slowly but surely (simply due to health). Caffeine, like tobacco doesn't cause permanent brain paralysis. So we're left with alcohol... Although it isn't a harsh carcinogen, it can cause liver diseases and kidney failure; on the up side, it's extensively used in cooking and throughout history as a way to liquify food/calories (the saying "I'm drinking my dinner" really isn't that far from the truth). Marijuana on the other hand is known to be worse than tobacco for cancer and causes permanent brain paralysis... and is more likely than alcohol to further progress persons to the next "stage" of use. On top of this, the research for it's non-recreational use has been less than convincing.
Now, I feel as though this thread has been hi-jacked way too much as it is. I'm done discussing; if you want to retort, be my guest; it's a free country. But I'm done bantering about a subject wholly unrelated to exhaust. (well, I guess not WHOLLY... you do have to exhaust (read, exhale) the smoke)