Ok, I've been reading here and just wanted to add my impute.
First off I would like to say that I don't do any type of drug (unless you include the occasional Tylenol). I know lots of people that smoke cigarettes, and plenty of people that smoke pot. I personally find absolutely nothing wrong with these, unless they are blowing the smoke in my face.
IMO, the only difference between tobacco and marijuana is that tobacco only has ill effects. I've yet to hear a story where a cigarette helped with a headache, etc. Marijuana is taken the same way as a cigarette/tobacco (rolled, pipe, hookah/bong) so I find it no different. Every other drug (that I can think of) is taken a completely different way, or at least doesn't have the diversity of all three ways.
The reason I believe Marijuana is illegal while tobacco continues to be legal, is that marijuana is easier to grow than tobacco. That means, if they legalize it entirely (aka anyone can have it), then instead of buying it, people can just grow it and not get taxed. Basically it all boils down to money (doesn't it always?) and how if the rich can't take money from the poor, they won't let it happen.