The medical knowledge is very clear. Excessive use can have harsh side effects.
That's not true what-so-ever, where did you ever hear that marijuana has harsh side affects (there are side affects, it's not something I myself would take, but then again I wouldn't smoke a cigarette either - not up to me what people do tho
). Could you give me an idea of what you believe these harsh side-effects to be?
Alcohol and Tobacco doesn't have an attachment of full acceptance.
What do you mean? We have a culture of alcohol use, even if cigarettes (it's more the nicotine and other chemical btw) are somewhat out of vogue, i'm not exactly suggesting a pro-marijuna PR campaign by the government.
It would be completely backward thinking to allow another drug in the mix for sake a logical sequence of: if other drugs are allowed, then this should be.
So you don't think that people ever should have had access to alcohol or cigarettes? If so then sure, if you're all for keeping 'harmful' chemicals away from the public to that extent then I guess it would make sense for you to disallow marijuna (perhaps cafeen and excessively salty/sugary foods too?).
Medical knowledge at the time keeps changing and making laws will simply be very difficult to continually pass after the completion of new studies.
No I don't think Medical knowledge on marijuna does keep changing the way you seem to be making out, at least I wasn't able to see any of this when I looked into it myself. Anyway, even if I'm wrong, medical knowledge of many things changes, generally tho a society will go with the best knowledge they have at the time and wait for a new development.
The fact is laws must reflect society and a great deal of society find drugs such as marijuana offensive and they request the law intervene.
So law should reflect majority opinion in your opinion? Anyway my reply is that a decent amount of society has/is using this drug and they're generally not hurting anybody by doing so.