I think those of us who have, ahem, been around for awhile can provide a unique view on pot. We were the kids of the sixties and seventies and most of us were exposed to drugs pretty heavily in college...whether or not we partook. For the record, I did not.
However, many many people I know did, including some of my relatives. I remember what they were like before they started smoking and what they were like after. There was just something missing. Some people who were really sharp before they used pot had short- and longterm memory problems. Apparently, it doesn't take very long for pot to affect retention. I've taught in a corrections institution biweekly for 14 years and teenagers who have smoked pot for just a couple of years can hardly remember the contents of a paragraph they just read. Frequently, their teachers from their old schools assure us they weren't like that before they started smoking weed.
Also, anyone who has driven with someone who was high has probably seen that that person was as bad a driver as any drunk. I certainly had the crap scared out of myself on several occasions like that. I don't care to have anyone whose driving is impaired out on the road.
Sugar and spice, I don't understand what cerebral palsy had to do with your friend's mother being terminal--CP doesn't kill.