By all accounts it seems Cannabis is
far less harmful (not "no worse than") alcohol. For starters it's never killed anybody, how many millions does alcohol (& cigarettes) kill every year?
Regarding the "teens will use it" argument. Well, they already
are, it's readily available everywhere. There's a good argument that making it legal will make it harder to obtain for any one under the legal age (remember, no one is arguing to make it legal for kids & teens to use), dealers don't check for I.D.
I'd like to direct you to Joe Rogan, 46 year old martial artist, comedian, UFC commentator & podcaster:
http://instagram.com/p/jupeQzpyEX/#
Always striving to learn more and better himself in his crafts.
In fact, go to youtube, search "joe rogan george st pierre turning side kick" (I can't post it because of swearing) and watch him teach GSP how to do some kicks properly.
He uses Cannabis regularly (and I do mean
regularly, though he didn't start using until his 30's), and cites it, and other psychedelic drugs, as a big reason for becoming a more thoughtful & nicer person (how's that for "profound effect"?). You should check out his podcast, he's high in many (maybe even most) episodes.