You said, "And yes, it can lead to harder drugs. My pot smoking crowd (who thankfully like myself has grown up and out of it) did occassionally harbor the opportunity to try other things like coke and acid. Someone in pot smoking group will always be the one to do the introducing of other drugs."
Right. So the main problem is obviously (in my opinion) not the substance itself...the problem is the people you choose to hang out with while acquiring and taking the substance...and your own attitude toward things in general, which was my point.
Pot is not the problem. People's addictive attitude toward things is the problem. Some people are inclined toward substance abuse and abuse of their health and doing reckless things. Those people will find something else harmful to injest or do in the absence of pot...and they do. It's often something much more harmful than pot.
The important thing is not to allow it to be mass marketed. You cannot stop people from casually acquiring, growing, and using marijuana with ANY law, unless you wish to assign a cop to watch every single citizen 24 hours a day, which is not possible. Anyway, someone else would have to watch the cop! :-) Cops sometimes deal illegal drugs too.