Stop what, having an objective based opinion? maybe you want to learn something? instead of pretending the cannabis plant is a gift from the gods, the cure to all illness, no downside. Your opinion is it should not be illegal to grow a plant ''coz you said so''. I know plenty of coke/e/trip takers who think that should be legal, gun owners who think that should be legal. It gets messy when you want to change laws simply because they suite you, never mind the negative effects it will have on others.
My fathers best friend works within the mental health sector, most of the psychosis he comes across is related to cannabis, but in high amounts, almost rasta style. With legalization comes liberal views over time, more people smoking who normally would not, people smoking more than they might normally. Add to that strains are getting stronger and people are using concentrates more commonly. Then you have the conditions for new or casual smokers to be smoking as much as rastafarians do on a % value, given lower intolerances, drug induced psychosis follows. Legalise it today and a spike in psychosis will be notably clear within 5 year (and I refer back to that poor dutch kid).
I guess psychosis is worse case, I know a lot of long time heavy smokers and they are not psychotic but also not with ought issues. They are very irritable, angry, unpleasant to be around unless they are high. They can not sleep well unless high, they have shocking memory's, sure sound like employees of the month materiel. So legalise it, are those guys ok to be that stoned at work operating machinery next to you?, if not..do you want to work with them when they are angry horrible bastards all day?. I do know one guy who owns a £million+ business but he was extremely lucky to walk into it, others run it for him.
I don't belittle anybody, just speaking objectively as possible based on the reality of all industry. Capitalism has been around for a long time now, family's and large corps have established themselves, land, patents, infrastructure, contracts have been bought etc. A kid leaving uni today does not have a equal footing to a kid 100 year ago, not the same cards, capitalism is the best system we have but it's monopolised now. Small and medium businesses fight for scraps or do some innovation then big corps devour the rewards (watts app). Asda has took over local fruit and veg shops, a lot of clothing, electrical, etc. To say a man wanting to start a fruit store has a better chance now than ever is an utter lie, most shopping centres are dying due to the likes of asda but also the internet ofc. Speaking of the internet, don't you see the corps slowly taking over it? you tube is all about big business adverts now, face book much the same.
I wish the best of luck to you friend, I truly do, but it's one hell of a gamble. Growing cannabis isn't an innovation, not like watts app was, the infrastructure is already in place for bigger corps. He will have to do something very special to survive. Again, best of luck to him.